Motor vehicles – Power – Electric
Reexamination Certificate
1998-05-18
2001-03-06
Johnson, Brian L. (Department: 3618)
Motor vehicles
Power
Electric
C180S065600
Reexamination Certificate
active
06196345
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electrically driven vehicles, and more particularly to such vehicles in which an axle shaft connects the electric motor to a drive wheel.
BACKGROUND OF THE INVENTION
Electric vehicles are coming into increasing importance because of their supposedly low environmental impact. When a heavyweight vehicle such as a truck or bus is fitted with an electric drivetrain driving the drive wheels through a speed reducing differential and one or more axles, it has been found that acceleration from low speeds is not smooth. Analysis of the perturbations in acceleration have shown that the stiffness of the axle shafts which couple torque to the drive wheels is such that the axle tends to twist, which, in conjunction with the very low friction of the electric drive train, results in oscillations of the vehicle speed.
Smoothly accelerating electric vehicles are desired.
SUMMARY OF THE INVENTION
A motor vehicle according to an aspect of the invention includes a source of electric energy, and an electric motor including an output shaft. The vehicle also includes a control which is a source of operator-controlled commanded torque signals. A control system is coupled to the source of electric energy, to the electric motor, and to receive torque command signals, for controlling the motor to produce the commanded torque at the output shaft of the motor. The vehicle further includes a mechanical gearbox including an input shaft coupled to the shaft of the motor and also includes an output shaft. The gearbox reduces the input shaft speed to produce a lower output shaft speed, with a concomitant increase in the output shaft torque. A drive wheel supports and drives the vehicle. An elongated axle shaft is coupled to the drive wheel and to the output shaft of the gearbox, for thereby coupling torque to the drive wheel from the gearbox. The axle shaft has a stiffness which, in conjunction with the mass of the vehicle, tends to produce undesired jerky motion of the vehicle. A motor speed sensor produces signals representative of the speed of the motor. A differencing arrangement includes a noninverting input port coupled to the source of operator-controlled commanded torque signals, and also includes an inverting input port, for subtracting signals applied to the inverting input port of the differencing arrangement from the commanded torque signals, for generating the torque command signals. A damping signal generator is coupled to the motor speed sensor and to the inverting input port of the differencing arrangement, for coupling to the inverting input port of the differencing arrangement at least the low-frequency components of motor acceleration.
In a particular embodiment of the invention, the gearbox is a differential including a second output shaft, and the vehicle further comprises a second drive wheel, and a second axle coupling the second drive wheel to the second output shaft of the differential.
The damping signal generator may include an infinite-impulse-response transversal filter including an input port coupled to the motor speed sensor, for receiving the motor speed signals, for generating the damping signals.
The infinite-impulse-response filter may include a delay stage including an input node coupled to receive the motor speed signals, and also including an output port at which delayed motor speed signals appear. A first summing circuit including an inverting input port and a noninverting input port, and an output port at which the difference between the signals applied to the inverting and noninverting input ports is generated. A second summing circuit includes an inverting input port, and also includes a noninverting input port coupled to the output port of the first summing circuit. The second summing circuit further includes an output port at which the damping signals are generated. A first multiplier is coupled to the input node of the delay stage and to the noninverting input port of the first summing circuit, for coupling the motor speed signals from the node to the noninverting input port of the first summing circuit with at particular gain. A second multiplier is coupled to the output port of the delay stage and to the inverting input port of the second summing circuit, for coupling the delayed motor speed signals from the output port of the delay stage to the inverting input port of the second summing circuit with a second gain. The second gain may equal the particular gain. A feedback path is coupled to the output port of the second summing circuit and to the inverting input port of the first summing circuit. The feedback path includes a delay stage and a third multiplier for multiplying feedback signals traversing the feedback path by a third gain.
REFERENCES:
patent: 1017198 (1912-02-01), Bender
patent: 3184662 (1965-05-01), Wallace
patent: 5349278 (1994-09-01), Wedeen
patent: 5404418 (1995-04-01), Nagano
patent: 5545957 (1996-08-01), Kubo et al.
patent: 5729111 (1998-03-01), Ogura et al.
patent: 5773938 (1998-06-01), Seong et al.
patent: 5784742 (1998-07-01), Giuliani et al.
patent: 5785191 (1998-07-01), Feddema et al.
patent: 5821720 (1998-10-01), Deng et al.
Infinite Impulse Response Filters (http://svr-www.eng.com.ac.uk/), Oct. 13, 1999
11R Filters (http://www.bores.com/), Oct. 13, 1999.
Gataric Slobodan
Lyons Arthur Paull
Bae Systems Controls Inc.
Fischmann Bryan
Johnson Brian L.
Krauss G. H.
Meise W. H.
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