Actuator for rear axle slip angle control
The following components are installed in the actuator:
- Servomotor
- Rotor position sensor
- Steering tie rod position sensor
| Index | Explanation |
|---|---|
| 1 | Actuator for rear axle slip angle control |
| 2 | Plug connection for steering tie rod position sensor (4-pin) |
| 3 | Plug connection for servomotor (three-pin) |
| 4 | Plug connection for rotor position sensor (4-pin) |
Servomotor
The electromechanical actuator consists of a servomotor that moves both track rods via a spindle gear drive. The track rods are connected to the track-rod arms. The actuator is configured for a maximum lifting movement of 8 mm, which leads to an angle of maximum 3° on the wheel. The spindle gear drive of the rear-wheel steering is designed as self-inhibiting. Following a system failure, the vehicle has the same characteristics as if designed without rear-wheel steering.
The servomotor is a brushless three-phase motor. The servomotor on the planetary gearbox with overriding function is supplied over 3 phases (= lines) with voltage (U, V, W). In the event of a short circuit, the servomotor can continue rotating due to external forces (no servomotor lock present). The consequence is an inconsistent steering wheel angle of up to 45° that can be perceived by the driver!
| Index | Explanation |
|---|---|
| 1 | Track rod joint, left |
| 2 | Nut |
| 3 | Servomotor |
| 4 | Track rod joint, right |
| 5 | Plug connection for servomotor |
| 6 | Threaded spindle |
Rotor position sensor
The rotor position sensor consists of a magnetoresistive element and a permanent magnet. The permanent magnet is located on the front of the rotor shaft of the servomotor. The magnetoresistive element measures the direction of the magnetic field horizontally and vertically. The rotor position sensor has a measuring range of 180°. The rotor position sensor supplies 2 voltage signals. A rotation through 360° is based on 2 signal sequences. The two voltage signals are used to calculate the position of the rotor. The number of half turns is counted by the HSR control unit, which stores this number in its memory when the ignition is switched off.
Steering tie rod position sensor
The steering tie rod position sensor is a non-contact position sensor (PLCD = Permanentmagnetic Linear Contactless Displacement). The steering tie rod position sensor consists essentially of a special core of soft magnetic material. This core is wrapped in a coil (primary coil) along its entire length. The core has another short evaluation coil on each end. A permanent magnet approximated to the sensor leads to local magnetic saturation. This enables a position to be determined.