Supplier Hitachi Astemo said it had developed a prototype of an anti-jerk control for EVs claimed to improve ride comfort by reducing the ‘back and forth jerk’ which occurs when the vehicle stops, and a motor torque control (motor ABS (anti-lock braking system) said to reduce electricity consumption, improve driving stability and impart a sense of security by maintaining appropriate wheel slippage during regenerative braking on slippery surfaces.
“In automobile operation, during deceleration when bringing a vehicle to a stop, braking force must be controlled by loosening or strengthening the brakes appropriately according to the speed, or else jerks will occur, resulting in shaking that impairs ride comfort,” the company said.
Unlike the torque of an internal combustion engine, the torque of an electric motor is highly responsive to the driver’s operation and can be increased quickly when accelerating or decelerating. Electric vehicles are also equipped with regenerative braking, which converts the torque into electric energy when the accelerator pedal is released. It quickly reduces the motor’s rotation with torque and it generates electricity while uses torque for the braking force.
The anti jerk control system that takes advantage of the motor’s torque characteristics and the braking power of regenerative braking and will suppress jerks by appropriately controlling the amount of torque to optimise the motor’s braking power when the accelerator pedal is released.
“With this control, even ordinary drivers can easily achieve smooth stops with little jolting achieving the same results as those of a skilled driver,” Hitachi Astemo said.
When driving on icy and slippery road surfaces, the regenerative braking alone could cause the tyres to slip, which in turn reduces steering and driving stability. One way to avoid this issue is to stop the regenerative brake operation, which can suppress tyre slippage, but this will reduce the amount of regenerated electric energy, which will worsen electricity consumption.
So the supplier developed a motor torque control technology which does not stop the regenerative brake itself, but controls the torque of the drive motor according to the driving conditions. The technology enables the vehicle to continue regenerating electricity, even during deceleration when the accelerator pedal is released, while controlling tyre slip and stabilising the driving condition.
This enables both regeneration of electricity and “a sense of security due to improved driving stability during deceleration”, the company added.
“The two newly developed technologies will contribute to OEMs’ electric vehicle development combining high driving performance with environmental performance, and thereby contribute to the popularisation of electrified vehicles.”