Adaptive Variable Suspension System
SUSPENSION CONTROL: ADAPTIVE VARIABLE SUSPENSION SYSTEM: SYSTEM DIAGRAM
SYSTEM DESCRIPTION
1. SYSTEM DESCRIPTION
(a) Absorber Control ECU
* The shock absorber damping force can be switched individually for each of the four wheels using the information from the sensors, and the set mode can be selected by operating the absorber control switch.
* Damping force switching controls are as follows: control according to vehicle speed, which is determined by driving conditions; anti-dive control; anti-squat control; rolling control; shudder control (Infinity control), which is controlled according to vehicle movement (road surface); bumpy control; and spring-bottom vibration control (unsprung damping control). Further, there is also a VSC cooperative control for VSC operations.
* Accurate damping force control is achieved by using nonlinear Infinity control based on the current theory in shudder control. The frequency of the bumps and shudders are monitored using signals from the acceleration sensor assembly, and the frequency of unsprung resonance is monitored using signals from the wheel speed sensors to achieve smooth damping control performance commensurate with driving status.
(b) Speed Sensor Control
* A smooth ride at low speed and operability and stability at high speed are balanced by making optimum settings of the damping force commensurate with vehicle speed based on wheel speed sensor information.
(c) Anti-dive Control
* The anti-dive control assures operability and stability (smoothing dive due to speed changes during deceleration) by accurately controlling damping force commensurate with the chassis dive status detected during braking using speed signals from the wheels and signals from the stop light switch.
* Operability and stability during braking and a smooth ride are assured by setting the damping force to high if deceleration G is great and when the driver has released the brake pedal.
(d) Anti-squat Control
* The hybrid control ECU detects the driveshaft torque and performs anti-squat control, which reduces vehicle squat and improves operability and stability, by accurately controlling the damping force.
(e) Rolling Control
* Operability and stability during cornering are achieved by controlling the damping force commensurate with the level of the lateral acceleration calculated using the turning angle signals from the steering angle sensor and the vehicle speed signals from the wheel speed sensors.
* The outer damping force caused when a wheel turns inward or outward (for all 4 wheels independently) is controlled by using control theory according to the rolling control model for the absorbers (for roll suppression and bound suppression), which suppress movement in 2 directions from a virtual point when a wheel is turned inward, as described in the diagram below. This enables excellent operability and stability, and assures turning and tracking performance and wheel-to-ground contact by optimizing the wheel status during rotation.
(f) Shudder Control (Infinity Control)
* If shudder in the roll and pitch directions is small, the shudder can be controlled by increasing the damping force for a specified time. If the shudder is great, the ride will lose its smoothness if the damping force only is properly increased. Consequently, to balance high damping performance and optimum ride smoothness, shudder control that applies the nonlinear Infinity control theory is used.
* Three acceleration sensors are used to detect sprung acceleration over road surface unevenness, and used to calculate the suspension stroke status by applying current control theory. The target damping force is calculated from these loads using Infinity control theory, and the damping force is then controlled for all four wheels independently.
* In order to control the sprung acceleration, the shock absorber varies the damping force to regulate the energy ratio of the sprung acceleration at the set value based on the road surface.
* If the vehicle status is controlled by using shock absorber damping force only, and if the damping force varies greatly, shudder can easily occur in the sprung acceleration.
* Natural and smooth shudder control is achieved in the sprung damping by applying nonlinear Infinity control theory.
(g) Bumpy Control
* If the frequency between the sprung resonance and unsprung resonance (bump frequency) is detected by using signals from the acceleration sensor while driving on a rough road surface in which shudder and bumps occur simultaneously, the damping force is set comparatively low to achieve a smooth sensation within the vehicle without the smooth ride being affected.
(h) Spring-Bottom Vibration Control (unsprung damping control)
* If unsprung resonance is detected by using signals from the wheel speed sensors, the unsprung resonance is controlled by increasing the damping force for a fixed period to achieve high road surface contact without the smooth ride being affected.
(i) VSC Operation Control (VSC cooperative control)
* The VDIM (VSC) effectiveness can be maximized by suitably switching the damping force commensurate with changes in the road surface micro and the vehicle lateral skid, using signals from the skid control ECU.
2. DAMPING FORCE CHARACTERISTICS
(a) Two modes, NORMAL and SPORT, can be selected by operating the absorber control switch.
(b) NORMAL is the mode that gives the highest priority to a comfortable ride. Damping force is lowest when driving under normal conditions.
(c) SPORT is the mode in which damping force is set higher, even when driving under normal conditions. SPORT further improves the driving performance and stability by utilizing wider area of high damping force, even when the damping force is affected by the driving and road conditions.
3. FAIL-SAFE FUNCTION Fail-Safe Chart
(a) When a failure occurs in the AVS (Adaptive Variable Suspension System) system, the absorber control indicator light comes on and AVS operation is prohibited.
4. DATA LIST/ACTIVE TEST Adaptive Variable Suspension System
(a) DATA LIST
According to the DATA LIST displayed on Techstream, the value and status of the switch, sensor, ECU, etc. can be read without removing parts.
Reading the DATA LIST as the first step in troubleshooting is one way to save time.
(b) ACTIVE TEST
Performing the ACTIVE TEST using Techstream allows the relay, ECU, etc. to be operated without removing parts.
Performing the ACTIVE TEST as the first step in troubleshooting is one way to save time.
5. FUNCTION OF COMPONENTS
