Tham khảo tài liệu 'understanding automotive electronics 5e episode 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | VEHICLE MOTION CONTROL 8 The variation in shock absorber damping is achieved by varying the aperture in the oil passage through the piston see Chapter 1 for discussion of shock absorber configuration . In practical semiactive suspension systems there are two means used to vary this aperture size a solenoid-operated bypass valve and a motor-driven variable-orifice valve Figure . Figure is an illustration of the force relative velocity characteristics of a shock absorber having a solenoid-switched aperture. The control system for a typical semiactive electronic suspension system has a similar configuration to any electronic control system as depicted in the block diagram of Figure . The control system typically is in the form of a microcontroller or microprocessor-based digital controller. The inputs from each sensor are sampled converted to digital format and stored in memory. The sampling is typically at about 500 Hz. In this control configuration sensors are provided to measure body sprung mass acceleration the relative position and motion of the wheel body unsprung sprung mass the steering wheel input and vehicle speed. The body acceleration measurement can be used to evaluate ride quality. The controller does this by computing a weighted average of the spectrum of the acceleration. The relative body wheel motion can be used to estimate tire normal force. Under program control in accordance with the control strategy the electronic control system generates output electrical signals to the actuators in Figure Adjustable Shock Absorber UNDERSTANDING AUTOMOTIVE ELECTRONICS 289 8 VEHICLE MOTION CONTROL Figure Force versus Relative Velocity of a Solenoid-Switched Aperture Shock Absorber each shock absorber. These actuators vary the oil passage orifice independently at each wheel to obtain the desired damping for that wheel. There are many possible control strategies and many of these are actually used in production vehicles. For the purposes of
