Woodward VariStroke Remote Servo Hydraulic Power Cylinder

The shield connections for the Analog Output (terminal #20), CAN1 (terminal

#23), and CAN2 (terminal #29) are through capacitors only as indicated in the

wiring section of this manual.

The power supply section performs the EMI filtering on the (18 to 32) V (dc) input

voltage and generates controlled voltages for several electronics sub-systems.

The power supply system is monitored for proper operation. If input voltage or

internal power systems are detected outside of allowable operating ranges, a

diagnostic alarm will be enunciated.

Calibration and configuration of alarms and shut down and redundancy operation

are configurable via the PC Service Tool.

The primary demand and redundant demand / feedback input signals are

designed for a (4 to 20) mA control signal. Each input signal is EMC protected.

Discrete outputs are provided for alarm and shut down enunciation. An internal

LED also is illuminated when a fault condition is detected. Cover needs to be

removed to see this LED. The configurable discrete output can be customized to

output a variety of enunciations using the PC Service Tool. All of the discrete

outputs are configurable for normally-open or normally-closed action using the

PC Service Tool.

Hydraulic Power Cylinder

The VariStroke Remote Servo can be connected to any hydraulic cylinder,

however; proper operation requires that the VariStroke Stability Equation be

satisfied (see Chapter 2. Stability Specifications). In order to control cylinder

position, the Cylinder must be equipped with a position feedback sensor. The

position sensor must meet the following specifications:

 Output Signal: 4–20 mA

 Input voltage (provided by the VariStroke Circuit Board): 15 Vdc

 Update Rate: ≤1 ms

 Linearity: ±0.04% Full Stroke

 Current Drain: < 100 mA

 Sensor Length must not exceed 2 times the Cylinder Stroke Length

Cylinder Position Control

The cylinder position controller adjusts the hydraulic power cylinder position to

match the feedback signal to the demand.

Both the servo position controller and cylinder position controller are monitored to

ensure accurate tracking.

The position controller regulates a pulse width modulated (PWM) drive signal to

the actuator. The drive current to the actuator is regulated, transiently allowing up

to 10 A to be provided to move the actuator at its maximum speed and torque. A

steady-state current limit becomes active after a period of a few seconds to

protect the actuator and electronics.