PITCH CONTROL DEVICE FOR ELECTRIC VEHICLE

• US 20130116874A1
• Filed: 06/10/2011
• Published: 05/09/2013
• Est. Priority Date: 06/11/2010
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: Ichinose, Masanori, Yasuda, Tomohiko, Satou, Takayuki
• Granted Patent: US 8,862,300 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 7/18 Controlling the braking effect B60L7/12, B60L7/14, B60L7/16 take precedence
• CPC Class Codes: B60T 2230/04 Jerk, soft-stop; Anti-jerk, reduction of pitch or nose-dive when braking
• CPC Class Codes: B60T 8/00 Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force by changing number of effective brake cylinders in power brake systems B60T17/10
• CPC Class Codes: B60T 8/17555 specially adapted for enhancing driver or passenger comfort, e.g. soft intervention or pre-actuation strategies
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/18 including control of braking systems
• CPC Class Codes: B60W 2520/16 Pitch
• CPC Class Codes: B60W 30/02 Control of vehicle driving stability
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

To suppress a change in a vehicle'"'"'s attitude due to a pitch motion during vehicle braking, a pitch control device for an electric vehicle can prevent discontinuous negative acceleration from occurring at a moment of the vehicle stopping by appropriately controlling a braking force of the vehicle, thereby effectively controlling the pitch motion of the vehicle, and can enhance steering stability while ensuring riding comfort for passengers, even when traveling resistance significantly changes according to road surface gradient and when the vehicle weight significantly changes with increases/decreases in the number of drivers and in the quantity of goods loaded.

This pitch control device for an electric vehicle, configured to conduct pitch control for suppressing the change in the attitude of the vehicle due to the pitch motion of the electric vehicle, controls the vehicle so that a braking/driving torque command value that is output to a motor for driving the vehicle when the vehicle stops will be a traveling resistance equivalent torque that is a value obtained by converting a force needed to stop the vehicle on a sloped road surface and maintain the vehicle in a stopped condition, into a torque of the driving motor.

Claims

1. A pitch control device for an electric vehicle, configured to conduct control for suppressing a change in an attitude of the electric vehicle due to a pitch motion thereof while the vehicle is accelerating/decelerating by a driving motor, the device comprising:

a drive unit that calculates a braking/driving torque based upon a request for the acceleration/deceleration of the vehicle and outputs the calculated torque as a braking/driving torque command value to the driving motor; and

a torque correction value calculator that calculates a torque correction value for the braking/driving torque so that the braking/driving torque command value will be a traveling resistance equivalent torque that is a value obtained when a force needed to stop the vehicle on a sloped road surface and maintain the vehicle in a stopped condition is converted into a torque of the driving motor;

wherein the drive unit corrects the braking/driving torque in accordance with the torque correction value calculated in the torque correction value calculator, and outputs the corrected torque as the braking/driving torque command value to the driving motor;

wherein assuming that the braking torque is corrected and that the corrected braking torque is output as a braking/driving torque command value to the driving motor, the device calculates a time-integrated value of a negative acceleration of the electric vehicle, then when the time-integrated value of the negative acceleration agrees with a speed of the electric vehicle, actually starts the correction of the braking/driving torque, and outputs the corrected value thereof as the braking/driving torque command value to the driving motor.

2. The electric-vehicle pitch control device according to claim 1, wherein:

the traveling resistance equivalent torque is determined from a difference between the braking/driving torque calculated in accordance with the vehicle acceleration/deceleration request dictated by driver'"'"'s pedal-operating quantities, and a vehicle body inertia-equivalent torque calculated from a time-differentiated value of a speed of the electric vehicle.

4. The electric-vehicle pitch control device according to claim 1, wherein:

the torque correction value calculator has a correction function for calculating the torque correction value, and calculates the torque correction value in accordance with the correction function so that when the vehicle stops, the braking/driving torque command value becomes the traveling resistance equivalent torque.

5. The electric-vehicle pitch control device according to claim 1, wherein:

the torque correction value is calculated from a difference between a pitch quantity that is a magnitude of amplitude of pitch vibration, and a target pitch quantity calculated from an acceleration of the electric vehicle, a weight thereof, and the traveling resistance equivalent torque, or is calculated from a difference between a time-differentiated value of the pitch quantity and that of the target pitch quantity.

6. The electric-vehicle pitch control device according to claim 4, wherein:

the correction function is changed according to a particular change in magnitude of a weight of the electric vehicle over time.

7. The electric-vehicle pitch control device according to claim 4, wherein:

the correction function is changed according to a particular change in magnitude of the traveling resistance equivalent torque over time.

8. The electric-vehicle pitch control device according to claim 4, wherein:

the correction function is changed according to a particular over-time change in a pitch quantity which is a magnitude of amplitude of the pitch motion of the electric vehicle.

3. (canceled)