New Generation ABS Using Linear Flow Control and Motor Speed Control 2003-01-0254
Recent trends of research & development for vehicular ABS are focused on the NVH as well as braking performance. For the conventional systems, we used On-Off control strategy, which is composed of pulse-up pressure rise, pressure dump and pressure hold mode. The main problems associated with the discrete (On-Off) nature of this control are severe noise and vibration.
Especially, among the three pressure modes of conventional control, the pressure pulse-up is the major source of noise and vibration. To reduce pulse-up noise & vibration of ABS, we introduce Linear Flow Control (LFC) concept, which allows continuous pressure rise mode instead of pressure pulse-up. Continuous pressure rise can be obtained by controlling the magnetic force of solenoid valve, which needs current control of the solenoid valve. In this regard, we proposed using pulse width modulation (PWM) method to control the current and to compensate for the discrete nature of actuator dynamics by duty control.
Another source of noise and pedal kickback during ABS action is excessive pumping of brake fluid caused by unnecessarily high motor speed. Because the level of noise and vibration caused by the motor is directly related with the motor speed, we introduced a new Motor Speed Control (MSC) method that could compromise pumping performance and noise.
Our new generation ABS also achieves better performance in stopping distance compared with conventional control method by reducing average pressure dump and maintaining optimal slip band.
In this paper, we will present recent results of LFC & MSC for our new generation ABS in a view of performance and NVH.