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| Illustration 1 | g06266452 |
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Steering Control System (1) Machine ECM (2) Hydraulic oil temperature sensor (3) Steering encoder (4) Steering angle position sender (5) Steering shunt solenoid (6) Warmup solenoid (7) Steering control valve solenoid | |
Note: The blue lines in the above illustration indicate an input signal. The red lines indicate an output signal. The red and blue lines indicate two-way communication.
Note: The above illustration shows the general layout of the steering system. Refer to the machine electrical schematic for detailed wiring information.
Machine ECM (1) monitors input signals from the following components to control the steering system:
- Hydraulic oil temperature sensor (2)
- Steering encoder (3)
- Steering angle position sensor (4)
The above illustration shows the connections of the direct input signals in blue. Input signals are also sent through the CAN lines. CAN communication devices are shown with a blue-and-red-stripe connection in the above illustration.
Machine ECM (1) energizes steering shunt solenoid (4) when the steering system is enabled or when the warmup valve is energized.
Steering shunt solenoid (5) enables and disables the steering system. When the steering shunt solenoid is energized, the steering shunt valve is closed. In this case, oil from the steering pump is routed to steering control valve (7) and the steering system is enabled.
When steering shunt solenoid (5) is not energized, the steering shunt valve opens. In this case, hydraulic oil from the steering pump is sent to tank and the steering system is disabled.
When the electronic control system determines that the hydraulic oil temperature is below operating parameters, machine ECM (1) energizes the warmup valve solenoid (6).
Warmup valve solenoid (6) controls hydraulic pressure in the steering manifold and raises pressure to the setpoint of the steering relief valve. When the warmup valve solenoid is energized, hydraulic pressure increases to the setpoint of the steering relief valve. As hydraulic oil is forced through the relief valve, the oil heats up.
Steering encoder (3) includes an electronically controlled friction device to control the force required to turn the steering wheel. Machine ECM (1) transmits a signal to control the friction device. This device applies a variable force to the steering wheel that causes the wheel to resist turning. The friction device is activated when the steering system is enabled.
When the machine has reached the mechanical steering limit, the highest friction level is applied to lock the steering wheel. The friction level is proportional to the difference between the desired steering angle and the actual steering angle. The desired steering angle is determined by the steering encoder. The actual steering angle is determined by the steering angle position sensor. The friction level prevents the operator from turning the steering wheel faster than the machine can respond.
The steering system is a closed loop system that is position controlled. Steering angle position sensor (4) measures the angle of machine articulation and transmits this information to machine ECM (1).
Machine ECM (1) monitors the signals from the two steering sensors in steering encoder (3). The machine ECM counts the pulses in these signals. The phases of the signals are compared to determine the position and direction of rotation of the steering wheel.
Machine ECM (1) monitors inputs from steering angle position sensor (4) and steering encoder (3). Based on these inputs, the machine ECM sends signals to the steering system directional control valve (7).
Hydraulic temperature sender (2) monitors the temperature of the oil in the hydraulic tank and sends this information to machine ECM (1). When the hydraulic oil temperature is less than
If the steering system detects motion without an active steering command the steering system and propel system are disabled. An uncommanded movement detection (UCMD) fault is also logged. If the steering system detects motion that is opposite the commanded direction, a UCMD fault is logged and the steering system is disabled.