Horst, Folkert (Pierrefonds, CA)
Szklar, Oleh (St-Hubert, CA)
Doig, Kelly (Ottawa, CA)
Cass, George R. (Montreal, CA)
Bousquet, Jean L. (Montreal, CA)

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11/14/2005

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Cattron Intellectual Property Corporation (Sharpsville, PA, US)

246/187A

246/182B, 104/300, 246/187B, 104/295, 246/182C

B61L3/00

246/183, 246/186, 340/825.62, 246/182B, 340/825.72, 701/20, 340/825.69, 246/187B, 104/295, 701/19, 246/182R, 246/167R, 246/187R, 246/187A

0733035		July, 1903	Harding
1360150		November, 1920	Shannon
1437637	Distant electrical control means	December, 1922	Dunkelberger
1515948	Toy locomotive	November, 1924	Hammond, Jr.
1653172	Radiocontrol of engine speed	December, 1927	Hammond, Jr.
1765173	Remote control means for cranes	June, 1930	Morrow
1788815	Variable-speed gear mechanism	January, 1931	Tubach
1816628	Train stopping and speed controlling mechanism	July, 1931	Williams et al.
1923499	Automatic train control	August, 1933	Naken
1929297	Remote control system	October, 1933	Webb
2235112	Speed control for vehicles	March, 1941	Pulaski
2257473	Remote control system for toys	September, 1941	McKeige et al.
2278358	Remote control system for toys	March, 1942	McKeige et al.
2331003	Remote control circuit	October, 1943	Smith
2447669	Remote-control system	August, 1948	Riley
2513342	Radio remote-control system	July, 1950	Marshall
2523662	Remotely controlled photographic apparatus movable along a track	September, 1950	Miller
2576424	Automatic speed control for railguided vehicles	November, 1951	Sunstein
2643369	Modulated pulse remote control	June, 1953	Manley et al.
2649835	Automatic control of the movement of picturemaking equipment	August, 1953	Lierley
2708885	Separate remote control of toy train and carried accessory	May, 1955	Smith et al.
2709773	Remote control system with position indicating means	May, 1955	Getting et al.
2743678	Method of and system for the remote control of model railroads	May, 1956	Hibbard
2768331	Fail-safe speed control system	October, 1956	Cetrone
2769601	Automatic radio control system	November, 1956	Hagopian et al.
2780300	Remote variable control of vehicle speed	February, 1957	Beyer
2832426	Teledynamic system for the control of self-propelled vehicles	April, 1958	Seargeant
2948234	Remote control organization for a locomotive	August, 1960	Hughson
2951452	Remote control system for a trimming locomotive	September, 1960	Karlet
2961640	Automatic radio-transmitted brake application and release signalling apparatus for railway trains	November, 1960	von Behren
2993299	Remotely controlled trackless vehicle	July, 1961	Dingee, Jr. et al.
2998513	Train control system	August, 1961	Taczak et al.
3029893	Automatic vehicle control system	April, 1962	Mountjoy
3072785	Remote control system for vehicles	January, 1963	Hailes
3086319	Road traffic toy remote controlled	April, 1963	Frisbie et al.
3096056	Locomotive remote control system	July, 1963	Allison
3201899	Remotely controlled toy and track arrangement therefor	August, 1965	Toteff et al.
3205618	Remote control system for toy automobiles	September, 1965	Heytow
3218454	Vehicle control system	November, 1965	Hughson
3227870		January, 1966	Joyce
3229086		January, 1966	Allison
3239962	Remotely controlled electrically driven and steered toy vehicle	March, 1966	Toteff et al.
3253143	Locomotive control system	May, 1966	Hughson
3263625	Electrical control systems for point-to-point transit systems	August, 1966	Midis et al.
3268727	Computer control for transit system	August, 1966	Shepard
3293549	Radio communication system for control of locomotives	December, 1966	Patterson
3304501	Time delay circuit for briefly holding a selective call transmitter energized	February, 1967	Ruthenberg
3312818		April, 1967	Staples
3315613	Remote control for model train system	April, 1967	Leslie
3328580	Rapid transit speed control system	June, 1967	Staples
3355584	Train speed control system	November, 1967	Baughmao
3355643	Plural remote controllers for plural motors using a common power connection	November, 1967	Benson
3361082	Model train control system	January, 1968	Leslie
3368073	Train speed control system	February, 1968	Baughman
3374035	Brake control systems for multiple unit trains	March, 1968	Howard
3378817	Signalling systems	April, 1968	Vitt
3380399	Remote control and supervision system for a railroad train	April, 1968	Southard et al.
3384033	Semi-automatic locomotive control system	May, 1968	Ruff
3402972	Continuous pressure control system	September, 1968	Cooper et al.
3530434	CODED FREQUENCY VEHICLE IDENTIFICATION SYSTEM	September, 1970	Stites et al.
3539226	OVERRIDE-NULLIFYING SCHEME FOR TRAIN CONTROL SYSTEM	November, 1970	Barber
3553449	CENTRAL OFFICE CONTROL CIRCUITS FOR REMOTE CONTROL SYSTEMS	January, 1971	Hathaway
3583771	LOCOMOTIVE BRAKE CONTROL APPARATUS SUITED FOR REMOTE MULTIPLE-UNIT OPERATION	June, 1971	Dressler, Jr.
3593293	REMOTE CONTROL AND DATA LOGGING SYSTEM	July, 1971	Rorholt
3601605	CAB SIGNAL AND SPEED CONTROL FOR LOCOMOTIVES	August, 1971	Elder et al.
3610363	AUTOMATIC VEHICLE GUIDANCE SYSTEM	October, 1971	Hartley
3628463	SPEED-CONTROL DEVICE	December, 1971	Kwiatkowski et al.
3639755	REMOTE CONTROL OF A LOCOMOTIVE	February, 1972	Wrege
3646613	AUTOMATIC CARRYING SYSTEM	February, 1972	Matsumoto et al.
3650216	RAILWAY CAR SPEED CONTROL TRANSPORTATION SYSTEM	March, 1972	Harwick et al.
3652937	SPEED AND FAULT INDICATOR FOR A MODEL VEHICLE	March, 1972	Garrott
3655962	DIGITAL AUTOMATIC SPEED CONTROL FOR RAILWAY VEHICLES	April, 1972	Koch
3660653	RAILROAD CAR SPEED CONTROL MECHANISM	May, 1972	Peterson
3686447	REMOTE CONTROLLED MINIATURE-VEHICLE	August, 1972	Takalo
3687082	AUTOMATIC ELECTRIC POWER SUPPLY AND SPEED CONTROL SYSTEM FOR AUTOMATED DRIVERLESS VEHICLES	August, 1972	Burke, Jr.
3694650	CAR COUPLING MAXIMUM SPEED CONTROL SYSTEM	September, 1972	Coiner
3696758	LOCOMOTIVE SIGNALING AND CONTROL SYSTEM	October, 1972	Godinez, Jr.
3728565	DEVICE FOR SENSING THE DIRECTION AND SPEED OF A SHAFT	April, 1973	O'Callaghan
3811112	CONTROL COMMAND SECURITY IN BINARY REMOTE CONTROL	May, 1974	Hoven et al.
3840736	APPARATUS FOR CONTROLLING VEHICLES AT JUNCTION POINTS	October, 1974	Asano et al.
RE28306		January, 1975	Burke, Jr.
3870939	METHOD FOR CONTROLLING ACCELERATION AND DECELERATION OF A TRACTION MOTOR	March, 1975	Robert
3880088	Vehicle control system and method	April, 1975	Grant
3885137	Method and system for constant-speed running of vehicles	May, 1975	Ooya et al.
3904249	Remote control braking apparatus including jerk control	September, 1975	Crawford
3906348	Digital radio control	September, 1975	Willmott
3937431	Postioning apparatus for tracked transport vehicles with linear motor propulsion	February, 1976	Güntner
3941202	Digital speed control	March, 1976	Sorkin
3964701	Model railroad train control system	June, 1976	Kacerek
3980261	Speed governors	September, 1976	Hadaway
3994237	Power supply for realistic control of model railroad engines	November, 1976	Thomsen
4002314	Train vehicle speed control signal providing apparatus	January, 1977	Barpal
4005837	Circuit arrangement for controlling the propulsion, braking and station stopping function for a rapid transit train	February, 1977	Grundy
4005838	Station stop and speed regulation system for trains	February, 1977	Grundy
4013323	Remote control brake system for a railway train	March, 1977	Burkett
4015082	Multi-channel signal decoder	March, 1977	Matty et al.
4041470	Fault monitoring and reporting system for trains	August, 1977	Slane et al.
4056286	Remote control brake system for a railway train	November, 1977	Burkett
4063784	Two-pressure brake control valve for airbrakes	December, 1977	Pick
4066299	Apparatus for locating a malfunctioning brake control valve on train	January, 1978	Clements
4067264	Locomotive cab running boards	January, 1978	Ensink
4087066	Train protection and control system	May, 1978	Bahker et al.
4093161	Control system with improved communication for centralized control of vehicles	June, 1978	Auer, Jr.
4095764	Spot control type automatic train stop system utilizing ground control units common to more than one block signal	June, 1978	Osada et al.
4108501	Brake accelerator for air brake system of a railway vehicle	August, 1978	Hintner et al.
4118774	Locomotive speed control apparatus	October, 1978	Franke
4133504	System for protected data transmission to track-bound vehicles	January, 1979	Dobler et al.
4138723	Motor vehicle speed control system	February, 1979	Nehmer et al.
4139239	Brake accelerator for a fluid-pressure brake system having a brake control valve	February, 1979	Staüble et al.
4156864	Pressure switch checking device for locomotives	May, 1979	Ingram
4162486	Encoded electrical control systems	July, 1979	Wyler
4164872	Method for determining spinning or slipping of the wheels in propulsion vehicles without dead axles	August, 1979	Weigl
4179624	Carrier control method by using phase-pulse signals	December, 1979	Shindo et al.
4179739	Memory controlled process for railraod traffic management	December, 1979	Virnot
4189713	Remote control systems	February, 1980	Duffy
4190220	Method and apparatus for braking rail-guided vehicles automatically and accurately with respect to a deceleration distance	February, 1980	Hahn et al.
4235402	Train vehicle speed control apparatus	November, 1980	Matty et al.
4241331	Remote control system with proportional value transmission	December, 1980	Taeuber et al.
4266273	System for controlling track-bound vehicles forming a train	May, 1981	Dobler et al.
4303215	Device for controlling the stopping of a train	December, 1981	Maire
4331917	Speed and direction sensing circuit	May, 1982	Render et al.
4335381	Remote control of electrical devices	June, 1982	Palmer
4344138	Digital air brake control system	August, 1982	Frasier
4347563	Industrial control system	August, 1982	Paredes et al.
4347569	Wheel slip system	August, 1982	Allen, Jr. et al.
4349196	Computer control toy track system	September, 1982	Smith, III et al.
4352103	Industrial control system	September, 1982	Slater
4370614	Speed and direction detector	January, 1983	Kawada et al.
4402082	Automatic line termination in distributed industrial process control system	August, 1983	Cope
4410983	Distributed industrial control system with remote stations taking turns supervising communications link between the remote stations	October, 1983	Cope
4445175	Supervisory remote control system employing pseudorandom sequence	April, 1984	Cohen
4450403	Method and apparatus for determining rotational speed	May, 1984	Dreiseitl et al.
4456997	Facility for fail-safe data transmission between trackside equipment of a guideway and vehicles moving therealong	June, 1984	Spitza
4459668	Automatic train control device	July, 1984	Inoue et al.
4463289	Wheel slip control using differential signal	July, 1984	Young
4464659	Method and an apparatus for remote control of a vehicle or a mobile engine	August, 1984	Bergqvist
4475159	Method of storing vehicle operating condition parameters	October, 1984	Gerstenmaier et al.
4486839	Synchronous wheel-slip protection system	December, 1984	Mazur et al.
4487060	Railway brake pressure monitor	December, 1984	Pomeroy
4495578	Microprocessor based over/under speed governor	January, 1985	Sibley et al.
4498016	Locomotive governor control	February, 1985	Earleson et al.
4513604	Method and apparatus for indicating leakage in compressed air line	April, 1985	Frantz et al.
4519002	Controlling the operations of at least two devices	May, 1985	Amano
4525011	Vigilance safety control system	June, 1985	Wilson
4553723	Railroad air brake system	November, 1985	Nichols et al.
4572996	Control unit for model vehicles	February, 1986	Hanschke et al.
4588932	Slip-limiting control for rail vehicles	May, 1986	Riondel
4614274	Control system for automatic material handling crane	September, 1986	LaValle et al.
4620280	Intelligent driverless vehicle	October, 1986	Conklin
4621833	Control system for multistable suspension unit	November, 1986	Soltis
4641243	Computer-controlled interlocking system for a railway installation	February, 1987	Hartkopf et al.
4654881	Remote control system having symmetrical tone, send/receive signaling circuits for radio communications	March, 1987	Dolikian et al.
4665833	Miniature electric track and train	May, 1987	Fleishman et al.
4673911	Elevator remote-control apparatus	June, 1987	Yoshida
4687258	Remote control system for a locomotive	August, 1987	Astley
4710880	Vehicle speed control apparatus and method	December, 1987	Zuber
4723213	Control device for vehicle speed	February, 1988	Kawata et al.
4726299	Method and apparatus for controlling a vehicle	February, 1988	Anderson
4733616	Track-bound selfpropelled car conveyor	March, 1988	Kurtz
4733740	Automated guided vehicle system	March, 1988	Bigowsky et al.
4768740	Vehicle tracking system	September, 1988	Corrie
4775116	Control of craft under high-G pilot stress	October, 1988	Klein
4791254	Flow switch	December, 1988	Polverari
4793088	Multiple remote controlled down rigger and planing board system	December, 1988	Fortuna
4854529	Vehicle control system having two trackside signal lines	August, 1989	Osada et al.
4870419	Electronic identification system	September, 1989	Baldwin et al.
4872195	Remote control unit for radio/television transmitter station	October, 1989	Leonard
4893240	Remote control system for operating selected functions of a vehicle	January, 1990	Karkouti
4896090	Locomotive wheelslip control system	January, 1990	Balch et al.
4901953	Controller for railway vehicles	February, 1990	Munetika
4950964	Locomotive differential wheel slip control	August, 1990	Evans
4955304	Remote locomotive spotter control	September, 1990	Spenk et al.
5005014	System and method for optimally transmitting acknowledge back responses	April, 1991	Jasinski
5012749	Radio controlled material handling apparatus	May, 1991	Passage, Jr.
5018009	Arrangement for a remote-controlled track-guided picture transmission	May, 1991	Koerv
5029532	Control cab	July, 1991	Snead
5039038	Railroad communication system	August, 1991	Nichols et al.
5050505	Radio control device for track-travelling toy	September, 1991	Konno
5065963	Transporting train travel control system	November, 1991	Usui et al.
5085148	Toy with remote control track switching	February, 1992	Konno
5109543	Hardware interface and protocol for a mobile radio transceiver	April, 1992	Dissosway et al.
5172316	Computer controlled railway brake equipment	December, 1992	Root et al.
5172960	Brake control minimizing the number of brakes activated and optimizing wear conditions	December, 1992	Chareire
5188038	Railroad car derailment safety device	February, 1993	Shanley
5222024	Method of and apparatus for controlling vehicle speed	June, 1993	Orita et al.
5244055	Transport control apparatus for automated guided vehicles	September, 1993	Shimizu
5249125	Computer controlled railway brake equipment	September, 1993	Root et al.
5251856	Model train controller for reversing unit	October, 1993	Young et al.
5264789	Method of determining the direction of rotation of a member using a rotor having a predetermined pattern of exciter surfaces	November, 1993	Braun et al.
5284097	Ballast distribution, regulation and reclaiming railroad maintenance device	February, 1994	Peppin et al.
5369587	Computer controlled railway brake equipment	November, 1994	Root et al.
5376869	Electric vehicle drive train with rollback detection and compensation	December, 1994	Konrad
5408411	System for predicting behavior of automotive vehicle and for controlling vehicular behavior based thereon	April, 1995	Nakamura et al.
5412572	Computer controlled railway brake equipment	May, 1995	Root et al.
5474267	Method and device for a smooth and timely deceleration or stop in automatic train control	December, 1995	Kubota et al.
5479156	Vehicle security system responsive to short and long range transmitters	December, 1995	Jones
5590042	Independent brake control	December, 1996	Allen, Jr. et al.

CA670272	September, 1963
CA1245744	November, 1988
DE1580940	January, 1971
DE2052009	April, 1972
DE2160494	July, 1973
DE2528463	January, 1977
DE2628905	December, 1977
DE2633089	January, 1978
DE2635751	February, 1978
DE2640756	March, 1978
DE2741584	March, 1979
DE2848984	May, 1980
DE2925196	October, 1980
DE2921860	November, 1980
DE2943385	May, 1981
DE3026652	February, 1982
DE3112793	February, 1982
DE3040080	April, 1982
DE3047637	July, 1982
DE3126383	January, 1983
DE3208819	September, 1983
DE3540563	March, 1987
DE3702527	August, 1988
EP0030121	June, 1981			Transit vehicle control apparatus and method.
EP0102017	March, 1984			Vehicle stopping position detecting system.
EP0132467	February, 1985			A control system for an electrically driven vehicle.
EP0326630	August, 1989			Method for transmitting remote control signals on a single carrier frequency between autonomous transmitters and receivers in time multiplexe and arrangement for realization of this method.
EP0499515	August, 1992			Brake system for wheeled vehicle.
FR2542951	September, 1984
GB1179751	January, 1970
GB1353438	May, 1974
GB1406711	September, 1975
GB1430642	March, 1976
GB1430644	March, 1976
GB1430645	March, 1976
GB1485420	September, 1977
GB1501234	February, 1978
GB1501372	February, 1978
GB1526033	September, 1978
GB1543917	April, 1979
GB1543918	April, 1979
GB2024484	January, 1980
GB2035487	June, 1980
GB2054229	February, 1981
GB2107910	May, 1983
GB2159995	December, 1985
GB2167886	June, 1986
GB2186725	August, 1987
GB2188464	September, 1987
JP52105406	September, 1977
JP53064308	June, 1978
JP3104769	May, 1991			THIN DIAMETER PIPE CONNECTION COUPLING
JP04266538	September, 1992			VEHICLE MOVEMENT CHARACTERISTIC CORRECTING DEVICE
JP04364307	December, 1992			FIXED POSITION STOP CONTROLLER FOR TRAIN
RU669375	November, 1976
WO/1984/003672	September, 1984			METHOD FOR INCREASING THE NUMBER OF SIGNALS WHICH MAY BE TRANSMITTED FROM A GROUND STATION TO A RAIL VEHICLE
WO/1985/001258	March, 1985			RAILROAD COMMUNICATION SYSTEM

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Le, Mark T.

Zagorin O'Brien Graham LLP

More than one reissue application has been filed for U.S. Pat. No. 5,511,749. The present reissue application is a continuation of application Ser. No. 10/374,590, Reissue No. RE39,011, filed Feb. 26, 2003, which is a reissue application of U.S. Pat. No. 5,511,749.

What is claimed is:

1. A remote control system in connection with a locomotive including a main tank with compressed air under pressure, a pneumatic brake line in which compressed air flows, and a member applying tractive power, said remote control system comprising: a) a transmitter for generating an RF signal; and b) a slave controller mounted on-board the locomotive, said slave controller having a first sensor responsive to the pressure of the compressed air in the main tank of the locomotive and a second sensor responsive to the flow of compressed air in the pneumatic brake line, said slave controller being responsive to outputs of said sensors to enable application of tractive power to the locomotive only when the pressure in the main tank is above a predetermined level and the flow of air in the pneumatic brake line is below a predetermined level.

2. A remote speed control system in connection with a locomotive that includes a main tank with compressed air, a pneumatic brake line in which compressed air flows, a throttle having a plurality of settings allowing tractive power regulation, and a brake system having a plurality of settings allowing braking power regulation, said speed control system comprising: a transmitter generating an RF signal indicative of a desired speed of travel of the locomotive; and a slave controller mounted on-board the locomotive, said slave controller having: a) receiver means for sensing said RF signal and providing data relative to the desired speed of travel of the locomotive, b) a first sensor responsive to the pressure of the compressed air in the main tank of the locomotive, c) a second sensor responsive to the flow of compressed air in the pneumatic brake line of the locomotive, and d) processor means for receiving said data relative to the desired speed of travel of the locomotive from said receiver means, said processor means responsive to said first sensor means, to said second sensor means, and to said data relative to the desired speed of travel for generating a throttle setting signal causing the throttle of the locomotive to acquire a selected setting when the pressure of the compressed air in the main tank is above a predetermined level and the flow of compressed air in the pneumatic brake line is below a predetermined level.

3. A remote speed control system in connection with a locomotive that includes a throttle having a plurality of settings allowing tractive power regulation and a brake system having a plurality of settings allowing braking power regulation, said speed control system comprising: a transmitter generating an RF signal indicative of a desired speed of travel of the locomotive; and a slave controller mounted on-board the locomotive, said slave controller having: a) receiver means for sensing said RF signal and providing data relative to the desired speed of travel of the locomotive, b) velocity sensor means for generating data representative of an actual speed of travel of the locomotive, and c) processor means for receiving data relative to the desired speed of travel of the locomotive from said receiver means and generating a throttle setting signal causing the throttle of the locomotive to acquire a selected setting and a brake setting signal causing the brake system of the locomotive to acquire a selected setting, said processor means being responsive to said velocity sensor means and to said data relative to the desired speed of travel and generating one of said throttle setting signal and said brake setting signal correlated to a difference between the desired speed of travel and the actual speed of travel of the locomotive to change the actual speed of travel of the locomotive and diminish that difference.

4. The invention as claimed in claim 3, wherein said processor means includes means for comparing said data relative to the desired speed of travel of the locomotive with said data representative of an actual speed of travel of the locomotive and generating an error signal correlated to the difference between the actual and desired speeds, said throttle setting signal being a linear combination of said error signal, its derivative, and its integral.

5. The invention as claimed in claim 3, wherein said processor means includes means for comparing said data relative to the desired speed of travel of the locomotive with said data representative of an actual speed of travel of the locomotive and generating an error signal correlated to the difference between the actual and desired speeds, said brake setting signal being a linear combination of said error signal, its derivative, and its integral.

6. The invention as claimed in claim 3, wherein said velocity sensor means includes a first velocity sensor generating a first signal representative of a speed of travel of the locomotive and a second velocity sensor generating a second signal representative of a speed of travel of the locomotive, said processor means being responsive to a discrepancy between said first and second speed of travel signals and issuing a brake setting signal causing the brake system of the locomotive to apply braking power.

7. The invention as claimed in claim 3, wherein said slave controller has means for generating data representative of a direction of travel of the locomotive.

8. A remote coast control system in connection with a locomotive that includes a throttle having a plurality of settings allowing tractive power regulation and a brake system having a plurality of settings allowing braking power regulation, said coast control system comprising: a transmitter generating an RF signal providing a coast command to the locomotive; a slave controller mounted on-board the locomotive, said slave controller having: a) receiver means for sensing said RF signal and providing said coast command, b) means for generating data representative of a velocity variation of the locomotive with relation to time, and c) processor means receiving said coast command from said receiver means and generating in response to said data representative of a velocity variation of the locomotive with relation to time one of (i) a brake setting signal causing the brake system of the locomotive to increase braking power when said velocity variation denotes a positive acceleration, and (ii) a brake setting signal causing the brake system of the locomotive to decrease braking power when said velocity variation denotes a negative acceleration, said processor means controlling the velocity of the locomotive without effecting any application of tractive power; and wherein said brake setting signal generated when said velocity variation denotes a negative acceleration represents a non-nil brake system setting, whereby braking power is applied to the locomotive at all times when said velocity variation denotes one of a positive and a negative acceleration.

9. The invention as claimed in claim 8, wherein said brake setting signal is a linear combination of an error signal representing a difference between an actual velocity of the locomotive and a velocity of the locomotive measured at a previous moment, its derivative, and its integral.

10. The invention as claimed in claim 9, further comprising a velocity sensor measuring an actual speed of travel of the locomotive, said velocity sensor communicating actual speed of travel data to said processor means.

11. The invention as claimed in claim 8, wherein said brake setting signal generated when said velocity variation denotes a negative acceleration represents a non-nil brake system setting, whereby braking power is applied to the locomotive at all times when said velocity variation denotes one of a positive and a negative acceleration.

12. A remote control system in connection with locomotive that includes a throttle allowing tractive power regulation and a brake system allowing braking power regulation, said remote control system comprising: a transmitter generating an RF signal providing a drive command that signals the locomotive to move in a first direction of travel; a slave controller mounted on-board the locomotive, said slave controller having: a) receiver means for sensing said RF signal and providing data indicative of said drive command, b) sensor means for sensing a second direction of travel of the locomotive and generating data representative of a the second direction of travel of the locomotive, and c) processor means receiving said data indicative of said drive command from said receiver means and generating a throttle signal causing application of tractive power to the locomotive, said processor means also receiving said data representative of a the second direction of travel of the locomotive from said sensor means and generating a brake signal causing application of the brakes to stop the locomotive when the locomotive moves in said second direction of travel, said second direction of travel being a direction other than said first direction of travel.

13. The invention as claimed in claim 12, wherein said processor means generates said brake signal causing application of the brakes to stop the locomotive when the locomotive moves in the second direction of travel, said second direction of travel being a direction other than said first direction of travel, after a predetermined amount of time has elapsed from the application of tractive power to the locomotive.

14. The invention as claimed in claim 12 13, wherein said predetermined amount of time is about 20 seconds.

15. A remote drive control system in connection with a locomotive with rollback protection, the locomotive including a throttle allowing tractive power regulation and a brake system allowing braking power regulation, said remote drive control system comprising: a transmitter generating an RF signal providing a drive command that signals the locomotive to start moving in a first direction of travel; a slave controller mounted on-board the locomotive, said slave controller comprising: a) receiver means for sensing said RF signal and providing data indicative of said drive command, b) sensor means for sensing an actual direction of travel of the locomotive and for generating data representative of an the actual direction of travel of the locomotive, and c) processor means receiving said data indicative of said drive command from said receiver means and issuing a throttle signal causing application of tractive power to the locomotive, said processor means also receiving said data representative of an the actual direction of travel of the locomotive from said sensor means and generating a brake signal causing application of the brakes to stop the locomotive when the locomotive moves in the actual direction of travel and the actual direction of travel is a direction other than said first direction of travel, and a predetermined period of time has elapsed from the application of tractive power to the locomotive.

16. The invention as claimed in claim 15, wherein said predetermined period of time is about 20 seconds.

17. A remote coast control system in connection with a locomotive that includes a throttle having a plurality of settings allowing tractive power regulation and a brake system having a plurality of settings allowing braking power regulation, said coast control system comprising: a transmitter generating an RF signal providing a coast command to the locomotive; a slave controller mounted on-board the locomotive, said slave controller having: a) receiver means for sensing said RF signal and providing said coast command, b) means for generating data representative of a velocity variation of the locomotive with relation to time, and c) processor means receiving said coast command from said receiver means and generating in response to said data representative of a velocity variation of the locomotive with relation to time, while coasting in response to the coast command, one of (i) a brake setting signal causing the brake system of the locomotive to increase braking power when said velocity variation denotes a positive acceleration, and (ii) a brake setting signal causing the brake system of the locomotive to decrease braking power when said velocity variation denotes a negative acceleration, said processor means controlling the velocity of the locomotive without effecting any application of tractive power.

18. The remote coast control system as recited in claim 17 wherein, while said locomotive is coasting in response to the coast command, said processor means is operative to generate, in response to velocity data indicating a velocity below a predetermined speed, a brake setting signal causing the brake system of the locomotive to increase braking power to stop the locomotive.

19. The remote coast control system as recited in claim 18 wherein said predetermined speed is 0.5 miles per hour.

20. The remote coast control system as recited in claim 17, wherein said transmitter is further operative to convey a coast with brake command to said receiver means, said processing means being responsive to said coast with brake command to preclude application of tractive power to the locomotive and cause said brake system to be continuously applied during movement of the locomotive.

FIELD OF THE INVENTION

The present invention relates to an electronic system for remotely controlling a locomotive. The system is particularly suitable for use in switching yard assignments.

BACKGROUND OF THE INVENTION

Economic constraints have led railway companies to develop portable units allowing a ground based operator to remotely control a locomotive in a switching yard. The unit is essentially a transmitter communicating with a slave controller on the locomotive by way of a radio link. Typically, the operator carries this unit and can perform duties such as coupling and uncoupling cars while remaining in control of the locomotive movement at all times. This allows for placing the point of control at the point of movement thereby potentially enhancing safety, accuracy and efficiency.

Remote locomotive controllers currently used in the industry are relatively simple devices that enable the operator to manually regulate the throttle and brake in order to accelerate, decelerate and/or maintain a desired speed. The operator is required to judge the speed of the locomotive and modulate the throttle and/or brake levers to control the movement of the locomotive. Therefore, the operator must posses a good understanding of the track dynamics, the braking characteristics of the train, etc. in order to remotely operate the locomotive in a safe manner.

OBJECT AND STATEMENT OF THE INVENTION

An object of the invention is to provide a remote control system allowing the operator to command a desired speed and responding by appropriately controlling the throttle or brake to achieve and maintain that speed.

Another object of the invention is to provide a remote locomotive control system allowing for control of the locomotive from one of two different transmitters.

Yet another object of the invention is to provide a remote locomotive control system having the ability to perform a number of safety verifications in order to automatically default the locomotive to a safe state should a malfunction be detected.

SUMMARY OF THE INVENTION

As embodied and broadly described herein the invention provides a locomotive remote control system. The system has

• • a transmitter capable of generating a binary coded radio frequency signal representing commands to be executed by the locomotive and
  • a slave controller for mounting on-board the locomotive. The slave controller has
    • a) a receiver for sensing the radio frequency signal;
    • b) a processor for receiving the radio frequency signal; and
    • c) a velocity sensor for generating data representing velocity of the locomotive. The processor responds to the velocity sensor and to the RF signal to actuate either one of a brake of a locomotive or a tractive power of the locomotive in order to attempt maintaining a requested speed.

As embodied and broadly described herein the invention also provides a locomotive control system which has

• • a) a transmitter for generating a binary code RF signal; and
  • b) a slave controller mounted on-board the locomotive for receiving that signal, the slave controller selectively accepting commands from a first transmitter or from a second transmitter.

As embodied and broadly described herein the invention further provides a remote control system for a locomotive which has

• • a) a transmitter for generating an RF binary coded signal; and
  • b) a slave controller mounted on-board the locomotive. The slave controller includes
    • a first sensor responsive to pressure of compressed air in a main tank of the locomotive; and
    • a second sensor responsive to flow of compressed air in responds to output of the sensors to enable application of tractive power to the locomotive only when a pressure in the main tank is above a predetermined level and a flow of air in the brake line is below a predetermined level.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of the portable transmitter of the remote locomotive control system in accordance with the invention;

FIGS. 2 and 4 are side elevational views of the portable transmitter;

FIG. 3 is a front elevational view of the portable transmitter;

FIG. 5 is a functional block diagram of the portable transmitter;

FIG. 6 is a diagram of the signal transmission protocol between the portable transmitter and a slave controller mounted on-board the locomotive;

FIG. 7 is a functional block diagram of the slave controller mounted on-board the locomotive;

FIG. 8 is a diagram illustrating the temporal relationship between signal transmission and the operation of the receiver of the slave controller;

FIG. 9 is a diagram illustrating the temporal relationship between signal transmission from two portable transmitters and the operation of the receiver of the slave controller;

FIG. 10 is a detailed functional block diagram of the slave controller mounted on-board the locomotive;

FIG. 11 is a side elevational view of a velocity sensor for generating a pulse signal whose frequency is correlated to the speed of the locomotive;

FIG. 12 is a side elevational view of the velocity sensor shown in FIG. 11;

FIG. 13 illustrates the pulse output of the velocity sensor shown in FIGS. 11 and 12;

FIGS. 14a to 14 d are a flow charts of the logic implemented to control the speed of the locomotive;

FIGS. 15a and 15b are diagrams illustrating the variation with respect to time of the velocity of the locomotive and of variables used to calculate a throttle or brake correction signal;

FIG. 16a is a flow chart illustrating the logic for controlling the speed of the locomotive in a COAST speed setting;

FIG. 16b is a flow chart illustrating the logic for controlling the speed in COAST WITH BRAKE setting;

FIGS. 17a and 17b are flow charts of the logic for transferring the command authority from one remote control transmitter to another; and

FIG. 18 is a flow chart of the safety diagnostic routine performed on the braking system of the locomotive.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to the annexed drawings, the locomotive control system in accordance with the invention includes a portable transmitter 10 which generates a digitally encoded radio frequency (RF) signal to convey commands to a slave controller mounted on-board the locomotive. The slave controller decodes the transmission and operates various actuators on the locomotive to carry into effect the commands remotely issued by the operator.

FIGS. 1 to 4 illustrates the physical layout of the portable transmitter 10 . The unit comprises a housing 12 enclosing the electronic circuitry and a battery supplying electric power to operate the system. A plurality of manually operable levers and switches projecting outside the housing 12 are provided to dial-in locomotive speed, brake and horn settings, among others. The various controls on the portable transmitter are defined in the following table:

REFERENCE		TYPE OF
NUMERAL	FUNCTION	ACTUATOR
	14	Locomotive Speed	Multi-Position Lever
		Control
	16	Locomotive Over-	Multi-Position Lever
		ride
		Brake Control
	18	Reset	Push-Button
	20	Direction	Multi-Position Switch
		(Forward/Reverse/
		Neutral)
	22	Ring Bell/Horn	Toggle Switch
	24	Train Brake	Toggle Switch
		Control
	26	Power on/Lights	Multi-Position Switch
		Dim/Bright
	28	Status Request	Push-Button
	30	Time Extend	Push-Button
	32	Relinquish Control	Push-Button
		to Companion
		Portable
		Transmitter

A detailed description of the various functions summarized in the above table is provided later in this specification.

On the top surface of the housing 12 is provided a display panel 34 that virtually echoes the control settings of the portable transmitter 10 . The display panel 34 includes an array of individual light sources 36 , such as light emitting diodes (LED), corresponding to the various operative conditions of the locomotive that can be selected by the operator. Hence, a simple visual observation of the active LED's 36 allows the operator to determine the current position of the controls.

FIG. 5 provides a functional diagram of the portable transmitter 10 . The various manually operable switches and levers briefly described above are constituted by electric contacts whose state of conduction is altered when the control settings are changed. For instance, the push-buttons 18 , 28 , 30 and 32 , and the toggle switches 22 and 24 have electric contacts that can assume either a closed condition or an opened condition. The multi-position levers 14 and 16 , and the multi-position switches 20 and 26 , have a set of electric contact pairs, only a single pair being closed at each position of the lever or switch. By reading the conduction state of the individual electric contact pairs, the commands issued by the operator can be determined.

An encoder 38 scans at short intervals the state of conduction of each pair of contacts. The scan results allow the encoder to assemble a binary locomotive status word that represent the requested operative state of the locomotive being controlled. The following table provides the number of bits in the locomotive status word required for each function:

NUMBER OF BITS IN LOCO-
MOTIVE STATUS WORD	FUNCTION
3	Locomotive Speed
	Control
3	Locomotive Brake
	Control
1	Reset
2	Direction
	(Forward/Reverse/
	Neutral)
2	Ring Bell/Horn
3	Train Brake Control
1	Lights Dim/Bright
1	Status Request
1	Time Extend
1	Relinquish Control to Companion
	Portable Transmitter

The locomotive status word also contains an identifier segment that uniquely represents the transmitter designated to control the locomotive. The purpose of this feature is to ensure that the locomotive will only accept the commands issued by the transmitter generating the proper identifier.

Most preferably, the encoder 38 includes a microprocessor programmed to intelligently assemble the locomotive status word. The microprocessor continuously scans the electric contacts of the transmitter controls and records their state of conduction. On the basis of the identity of the closed contacts, the program will produce the function component of the locomotive status word which is the string of bits that uniquely represents the functions to be performed by the locomotive. The program then appends to the function component the locomotive identifier component and preferably a data security code enabling the receiver on-board the locomotive to check for transmission errors.

In a different form of construction, the encoder may be constituted by an array of hardwired logic gates that generate the locomotive status word upon actuation of the controls.

A transmitter 40 receives the locomotive status word and generates an RF signal for transmission of the coded sequence by frequency shift keying. In essence, the frequency of a carrier is shifted to a first value to signal a logical 1 and to a second value to signal a logical 0. The transmission protocol is best shown in FIG. 6 . Each transmission begins with a burst of the carrier frequency 42 for a duration of eight (8) bits (the actual time frame is established on the basis of the transmission baud rate allowed by the equipment). Each bit of the data stream is then sent by shifting the frequency to the first or the second value depending on the value of the bit, during a predetermined time slot 44 .

The transmitter 40 sends out the locomotive status word in repetition at a fixed rate selected in the range from two (2) to five (5) times per second. By providing the transmitter with a unique repetition rate, the likelihood of transmission errors is reduced when several portable transmitters in close proximity broadcast control signals to individual locomotives, as described below.

FIG. 7 provides a diagrammatic representation of the slave controller mounted on board the locomotive. The slave controller identified comprehensively by the reference numeral 46 has three main components, namely a receiver unit 48 , a processing unit 50 and a driver unit 52 . More particularly, the receiver unit 48 senses the locomotive status word sent out from the portable transmitter 10 , decodes the transmission and supplies the resulting binary sequence to the processing unit 50 . To achieve a reliable communication link, the receiver 48 is synchronized with the transmitter 40 at three different levels. First, the receiver circuitry defines a signal acceptance window that opens itself at the rate at which the locomotive status word is sent out by the respective controlling transmitter 40 . Second, the receiver 48 will observe the frequency value of the transmission in order to decode the binary sequence at intervals precisely corresponding to the time slots 44 . Third, the acceptance window opens in phase with the signal transmission.

The first two levels of synchronization are established through hardware designs, by setting the transmitter 40 and the receiver 48 to the same period of transmission/reception. On the other hand, the phasing of the receiver to the incoming locomotive status word transmission is effected through observation of the burst of carrier frequency 42 that begins each transmission cycle. The diagram in FIG. 8 graphically illustrates the relationship between the signal transmission and the signal reception. The time line 54 shows the successive transmission of the locomotive status word as a series of blocks 56 . The activity of the receiver 48 is shown on the time line 58 . The hatched areas correspond to the time intervals during which the receiver is not listening. At time t=0 the first locomotive status word is sent out by the transmitter 40 . The burst of the carrier frequency 42 is sensed by the receiver 48 which then activates the sequence of opening and closing of the signal acceptance window which is fully synchronized (in period and phase) with the signal transmission.

This characteristic is particularly advantageous when several transmitters broadcast simultaneously control signals to different locomotives in close proximity to one another. By setting each transmitter (and the companion receiver) at a unique transmission/reception period, secure communication links can be maintained even when all the transmitters use the same carrier frequency. FIG. 9 illustrates this feature. Time line 60 shows the transmission pattern of a first portable transmitter. The time line 62 depicts the window of acceptance of the companion receiver. The numeral 64 identifies the transmission pattern of a second portable transmitter. Assuming that both portable transmitters are actuated exactly at t=0, the signal received during the first opening of the window of acceptance will be corrupted since two locomotive status word transmissions are concurrent in time. However, the third and the seventh locomotive status word transmissions from the first portable transmitter will be clearly received since there is no overlap with the locomotive status words sent out by the second portable transmitter. Hence the purpose of providing each transmitter with a unique signal repetition rate reduces the likelihood of transmission conflicts.

It should be noted that the receiver 48 can, and probably will, correctly receive from time to time a locomotive status word from an unrelated transmitter. This status word will be rejected, however, because the transmitter identifier will not match the value stored in the memory of the slave controller.

The transmitter/receiver gear of the remote locomotive control system has been described above in terms of function of the principal parts of the system and their interaction. The components and interconnections of the electric network necessary to carry into effect the desired functions are not being specified because such details are well within the reach of a man skilled in the art.

FIG. 10 provides a functional diagram of the processing unit 50 . A central processing unit (CPU) 66 communicates with a memory through a bus 70 . A reserved portion memory 68 contains the program that directs the CPU 66 to control the locomotive depending on the several inputs that will be discussed later. The memory also contains a section allowing temporary storage of data used by the CPU when handling hardware events.

The current locomotive status and the commands issued from the remote transmitter are directed to the CPU through an interface 72 communicating with the bus 70 . The interface 72 receives input signals from the following sources:

a) A speed direction sensor 74 providing locomotive velocity and direction of movement data;

b) A speed sensor 76 providing solely locomotive velocity data. The speed sensor 76 provides the CPU 66 with redundant velocity data allowing the CPU 66 to detect a possible failure of the main speed sensor 74 .

c) A pressure sensor 78 observing the air pressure in the locomotive brake system;

d) A pressure sensor 79 observing the air pressure in the main reservoir;

e) A pressure sensor 80 observing the air pressure in the train brake system;

f) A sensor 82 observing the flow rate of air in the brake system of the train; and

g) The decoded locomotive status word generated by the receiver 48 .

The structure of the speed/direction sensor 74 is illustrated in FIGS. 11 and 12. The sensor includes a disk 84 mounted to an axle 86 of the locomotive. When the locomotive is moving the disk 84 turns at the same angular speed as the axle 86 . The disk 84 is provided with a layer of reflective coating 85 deposited to form on the periphery of the disk equidistant and alternating reflective zones 87 and substantially non-reflective zones 89 . A pair of opto-electric sensors 92 and 94 are mounted in a spaced apart relationship adjacent the periphery of the disk 84 . The sensor 92 comprises an emitter 92 a generating a light beam perpendicular to the plane of the disk 84 , and a receiver 92 b producing an electric signal when sensing the reflection of the light beam on the reflective zones 87 . However, when a substantially non-reflective surface 89 registers with the sensors 92 , the output of the receiver is null or very low. The structure and operation of the opto-electric sensor 94 is identical to the sensor 92 . Thus, the sensor 94 comprises an emitter 94 a and a receiver 94 b.

The spacing between the opto-electric sensors 92 and 94 is such that they generate output pulses due to the periodic change in reflectivity of the disk surface, occurring at different instants in time. As best shown in FIG. 10, and assuming that the disk 84 rotates in the counter clockwise direction, when the sensor 92 switches on as a result of a reflective zone 87 registering with the emitter 92 a and the receiver 92 b, the sensor 94 is still in a stable on condition and can be caused to switch off only by further rotating the disk 84 .

Preferably, the disk 84 and the sensors 92 and 94 are mounted in a hermetically sealed housing to protect the assembly against contamination by water or dirt.

FIG. 13 illustrates the signal waveforms produced by the opto-electric sensors 92 and 94 . Both outputs are pulse trains having the same frequency but out of phase by an angle α which depends upon the spacing of the sensors 92 and 94 . When the locomotive moves forward the disk 84 rotates in a given direction, say clockwise. In this case, the pulse train from sensor 94 leads the pulse train from sensor 92 by angle α. When the locomotive is in reverse, then the output of sensor 92 leads the output of sensor 94 by angle α (this possibility is not shown in FIG. 13 ). The processing unit 50 observes the occurrence of the leading pulse edges from the sensors 92 and 94 with relation to time to determine the identity of the leading signal, which allows derivation of the direction of movement of the locomotive.

Velocity data is derived by measuring the rate of fluctuation of the signal from any one of sensors 92 and 94 . It has been found practical to determine the velocity at low locomotive speeds by measuring the period of the signal. However, at higher speeds the frequency of the signal is being measured since the period shortens which may introduce non-negligible measurement errors.

The speed sensor 76 is similar to sensor 74 described above with two exceptions. First, a single opto-electric sensor may be used since all that is required is velocity data. Second, the speed sensor 76 is mounted to a different axle of the locomotive.

The pressure sensors 78 and 79 are switches mounted to the main reservoir and to the pneumatic line that supplies working fluid to the locomotive independent braking mechanism, and produce an electric signal in response to pressure. These sensors merely indicate the presence of pressure, not its magnitude. In essence, each sensor produces an output when the air pressure exceeds a preset level, indicating whether the reserve of compressed air is sufficient for reliable braking. Unlike the sensors 78 and 79 , the pressure sensor 80 is a transducer that generates a signal indicative of presence and magnitude of pressure in the train brake air line.

The airflow sensor 82 observes the volume of air circulating in the pneumatic lines of the train brake system. The results of this measurement along with the output of pressure sensor 78 provide an indication of the state of charge of the pneumatic network. It is considered normal for a long pneumatic path to experience some air leaks due primarily to imperfect unions in pipe couplings between cars of the train. However, when a considerable volume of air leaks, the airflow sensor 82 enables the processing unit to sense such condition and to implement corrective measures, as will be discussed later.

The interface 72 receives the signals produced by the sensors 74 , 76 , 78 , 79 , 80 , and 82 and digitizes them where required so they can be directly processed by the CPU 66 . The locomotive status word issued by the receiver 48 requires no conversion since it is already in the proper binary format.

The binary signals generated by the CPU 66 that control the various functions of the locomotive are supplied through the bus 70 and the interface 72 . The following control signals are being issued:

a) A signal 98 to set the lights of the locomotive to off/low intensity/high intensity. The signal is constituted by one (1) bit, each operative condition of the locomotive lights being represented by a different bit state;

b) A two (2) bit signal 100 to operate the bell or the horn or the locomotive;

c) A five (5) bit signal 102 for traction control. Four bits are used to communicate the throttle settings (only eight (8) settings are possible) and one bit for the power contacts of the electric traction motors;

d) An eight (8) bit signal 104 for train brake control. The number of bits used allows 256 possible brake settings; and

e) A seven (7) bit signal 106 for independent brake control. The number of bits used allows 128 possible brake settings.

The interface 72 will covert at least some of the signals 98 , 100 , 102 , 104 , and 106 from the binary form to a different form that the devices at which the signals are directed can handle. This is described in more detail below.

The actuators for the lights and bell/horn are merely switches such as relays or solid state devices that energize or de-energize the desired circuit. The interface 72 , in response to the CPU 66 instruction to set the lights/bell/horn in the desired operative position, will generate an electric signal that is amplified by the driver unit 52 and then directed to the respective relay or solid state switch.

With regard to the traction control it should be noted that most locomotive manufacturers will install on the diesel/electric engine as original equipment a series of actuators that control the fuel injection, power contracts and brakes among others, hence the tractive power that the locomotive develops. This feature permits coupling several locomotives under control of one driver. By electrically and pneumatically interconnecting the actuators of all the locomotives, the throttle commands the driver issues in the cab of the mother engine are duplicated in all the slave locomotives. The locomotive remote control system in accordance with the invention makes use of the existing throttle/brake actuators in order to control power. The interface 72 converts the binary throttle settings issued by the CPU 66 to the standard signal protocol established by the industry for controlling throttle/brake actuators. This feature is particularly advantageous because the locomotive remote control system does not require the installation of any throttle/brake actuators. As in the case of the lights and bell/horn signals 98 and 100 , respectively, the traction control signal 102 incoming from the interface 72 is amplified in the driver unit 52 before being directed to the throttle/brake actuators.

The train brake control signal 104 issued by the interface 72 is an eight (8) bit binary sequence applied to a valve mounted in the train brake circuit to modulate the air pressure in the train line that controls the braking mechanism. The working fluid is supplied from a main reservoir whose integrity is monitored by the pressure sensor 79 described above. The independent locomotive brake is controlled in the same fashion with binary signal 106 .

The operation of the locomotive control system will now be described with more detail.

SPEED CONTROL TASK

The flowchart of the speed control logic is shown in FIGS. 14a to 14 d. The program execution begins by reading the velocity data generated from sensors 74 and 76 that are mounted at different axles of the locomotive. The data gathered from each sensor is stored in the memory 68 and then compared at step 124 . If both sensors are functioning properly they should generate identical or nearly identical velocity values. In the event a significant difference is noted the CPU 66 concludes that a malfunction exists and issues a command (step 126 ) to fully apply the independent brake in order to bring the locomotive to a complete stop.

Assuming that no mismatch between the readings of sensors 74 and 76 is detected, the CPU 66 will compare the observed locomotive speed with the speed requested by the operator. The later variable is represented by a string of three (3) bits in the locomotive status word (the flowchart of FIGS. 14a to 14 d assumes that the locomotive status word has been correctly received, has the proper identifier and has been stored in the memory 68 ). The operator can select on the portable transmitter 10 eight possible speed settings, each setting being represented by a different binary sequence. The speed settings are as follows:

1) STOP

2) COAST WITH BRAKE

3) COAST

4) COUPLE (1 MILE PER HOUR (MPH))

5) 4 MPH

6) 7 MPH

7) 10 MPH

8) 15 MPH

If any one of settings 4 to 8 have been selected, which require the locomotive to positively maintain a certain speed, the CPU 66 will effect a certain number of comparisons at steps 128 and 130 to determine if there is a variation between the actual speed and the selected speed along with the sign of the variation, i.e. whether the locomotive is overspeeding or moving too slowly. More particularly, if at step 128 the CPU 66 determines that the observed speed is in line with the desired speed no corrective measure is taken and the program execution initiates a new cycle. On the other hand, if the actual speed differs from the setting, the conditional test 130 is applied to determine the sign of the difference. Under a negative sign, i.e. the locomotive is moving too slowly, the program execution branches to processing thread A (shown in FIG. 14 b). In this program segment the CPU 66 will determine at step 132 the velocity error by subtracting the actual velocity from the set point contained in the locomotive status word. A proportional plus derivative plus integral algorithm is then applied for calculating throttle setting intended for reducing the velocity error to zero. Essentially the CPU 66 will calculate the sum of the integral of the velocity error signal (calculated in step 145 ), of the derivative of the velocity error signal (calculated in step 147 ), and of a proportional factor (calculated in step 143 ). The latter is the velocity error signal multiplied by a predetermined constant. The result of this calculation provides a control signal that is used for modulating the throttle actuator of the locomotive through output signal 102 of the interface 72 .

FIG. 15a is a diagram illustrating the variation of the current velocity signal, the set point, the velocity error, the velocity error integral, the velocity error derivative and velocity error proportional with respect to time.

With reference to FIG. 14d, when the new throttle setting has been implemented the program execution continues to steps 134 and 136 where the current direction of movement and speed of the locomotive are determined from the reading of sensor 74 . In the event the CPU 66 observes a zero speed value for a time period of more than 20 seconds in spite of the fact that a tractive effort is being applied (step 138 ), it declares a malfunction and fully applies the independent locomotive brake. Normally, when a tractive effort is applied it causes the locomotive to accelerate. The movement, however, may occur after a certain delay following the application of the tractive effort especially if the locomotive is pulling a heavy consist. Still, if after a certain time period no movement is observed, some sort of malfunction is probably present. One possibility is that both sensors 74 and 76 have failed and register zero speed even when the locomotive is rolling. This is highly unlikely but not impossible. When such condition is encountered the CPU 66 immobilizes the locomotive immediately upon determination that a fault is present.

The 20 seconds waiting period before application of the independent brake is implemented by verifying the velocity data from sensor 74 during a certain number of program execution cycles. For instance, the current velocity value is compared to the velocity value observed during the previous execution cycle that has been stored in the memory 68 . If a change is noted, i.e. the locomotive moves, then the step 138 is considered to have been successively passed. If, however, after 200 execution cycles that require about 20 seconds to be completed, no change with the previously observed velocity value is noted, the independent brake is fully applied.

Assuming that motion of the locomotive is detected at step 138 , the program proceeds to step 140 where the direction of movement of the locomotive read from the output of sensor 74 is compared to the direction of movement specified by the operator. This value is represented by a four (4) bit string in the locomotive status word. If the locomotive is moving rearwardly while the operator has specified a forward movement, the CPU 66 detects a condition known as “rollback”. Such condition may occur when the locomotive is starting to move upwardly on a grade while pulling a heavy consist. Under the effect of gravity the train may move backward for a certain distance until the traction system of the locomotive has been able to build-up the pulling force necessary to reverse the movement. During a rollback condition the electric current in the traction motors of the locomotive increase beyond safe levels. Hence it is desirable to limit the rollback in order to avoid damaging the hardware. The program is designed to tolerate a rollback condition for no longer than 20 seconds. If the condition persists beyond this time period the independent brake is fully applied. The 20 seconds delay is implemented by comparing the evolution of the results of the comparison step 140 with the results obtained during the previous execution cycle; if the results do not change for 200 program execution cycles that require about 20 seconds of running time on the CPU 66 , a fault is declared and the brake applied.

In the case where both tests 136 and 140 are successively passed, i.e. the locomotive is moving in the selected direction, the program execution returns to the beginning of the cycle as shown in FIG.