. EXAMPLE OF THE EFFECT OF CONTROL
For example, on a slippery surface, if the vehicle tends to be under-steered contrary to the driver’s intention, a yaw moment (a rotational moment) is created to restrain the under-steering by increasing the rear-inside braking force. On the other hand, when the vehicle tends to be oversteered, a yaw moment (a restorative moment) is created to restrain the oversteering by increasing the front-outside wheel braking force. Furthermore, when it is determined that the vehicle is over-speeding, safe and stable cornering is enabled by deceleration from reducing the engine output.
. JOINT CONTROL
ASC transmits data necessary for control of ABS and TCL, performing joint control.
Even during ABS operation, ASC performance is improved from the joint operation of the stability control.
During acceleration, electric motor unit output is governed through joint operation with stability control.
This ECU incorporates the ABS function, EBD function, TCL function, and ASC function.
The hydraulic units of the ASC system employ the automatic pressurisation function. These systems also incorporates G and yaw rate sensor, steering wheel sensor, and master cylinder pressure sensor (integrated with hydraulic unit).
. STABILITY CONTROL DESCRIPTION
ASC-ECU detects vehicle movement based on information from various sensors and calculates a model of ideal vehicle movement. ASC-ECU compares the actual vehicle movement with the ideal vehicle model, and manages the brake of the specific wheel so that the actual vehicle movement gets close to the ideal vehicle mode. It also controls the understeer or oversteer condition by creating the yaw moment in the vehicle.
The stability control manages the vehicle attitude by creating a yaw moment from altering the balance between the cornering force and each wheel’s braking mechanism.
. TRACTION CONTROL DESCRIPTION
When the driving wheels slip on the slippery road surface, TCL applies the brake automatically, sends the signal requesting electric motor unit speed reduction to the EV-ECU, and prevents the loss of the driving force resulting from the slippage of the driving wheel.
. FAIL-SAFE AND DIAGNOSTIC FUNCTIONS
ASC-ECU constantly monitors the input and output signals. If an error is detected in the system, ASC-ECU sends a fail signal and the corresponding indicator lamp is illuminated or blinks. Various controls are processed depending on the cause of malfunction as shown below.
ASC-ECU has the following functions for easier system checks.
. Diagnosis code set
. Service data output
. Actuator test
. Freeze frame data output . Torque Sensor, Steering Warning,
To improve operational reliability, the dual-circuit system has been adopted for the torque sensor. If any malfunction occurs in the electric power steering system, the fail-safe function of the EPS-ECU is activated, and the output current of the EPS-ECU applied to the motor is turned off. At the same time, the steering system enters manual mode, and informs a driver of the system malfunction by illuminating the warning lamp on the combination meter. The warning lamp illuminates when the following malfunctions occur: open circuit in the electric power steering system wiring harness, poor connection, malfunctions in the EPS-ECU, motor, or sensors.
[url="http://scholar.google.com/scholar_url?hl=en&q=http://members.rennlist.com/jandreas/EvolutionOfVDC-BOSCH.pdf&sa=X&scisig=AAGBfm1FeLXizoUfrAutnE97xPDT1WlHvw&oi=scholarr"]Also reference:Vehicle Dynamic Behavior[/url] . ROAD REACTION TORQUE CONTROL
By estimating the steering reaction torque from the road surface based on each wheel speed information from ASC-ECU and the steering torque information from the torque sensor installed to the steering gear assembly, and optimising the corresponding return torque to the steering neutral direction, the road reaction torque control improves the steering wheel return control at low speed and the steering feel at high speed. . VEHICLE BEHAVIOR ESTIMATION CONTROL
By estimating the vehicle behavior during steering operation based on wheel speed information from ASC-ECU and the steering torque information from the torque sensor installed to the steering gear assembly for additional steering torque, the vehicle behavior estimation control improves the vehicle stability at medium- and high-speed steering.