Section 3. Systems OverviewToyota Model 7HBW23 Service Manual

Theory of Operation

(when travel is requested), Arm Angle B switch (S25) closes and enables slow speed travel. When the control handle is placed beyond 46° from the full upright position, Arm Angle A switch (S24) also closes, enabling fast speed travel. When the control handle is placed in the bottom 8° of its operating range, Arm Angle B switch opens, activating the parking brake.

Travel Request, Forks Trailing

When the thumb controls are rotated in the forward direction (tractor-first) from neutral:

•a forward travel signal is detected via hall effect sensors, converted into a travel instruction in the ETAC (See “Electronic Tiller Arm Card (ETAC)” on page3-7.) and transmitted via the Controller Area network (CAN) to the power amplifier.

•the ETAC verifies that the emergency reverse button is not activated before supplying the travel command to the power amplifier.

•the ETAC verifies that switch S25 (Arm Angle B) is engaged for slow speed mode.

•the ETAC verifies that both switch S24 (Arm Angle A) and switch S25 (Arm Angle B) are engaged for fast speed mode.

•the voltage at M– of the drive motor will vary from 24V to 1V. The voltage is proportional to the position of the thumb controls.

•the drive wheel starts to rotate in forward direction at a speed proportional to the voltage at M–.

Travel Request, Forks-First

When the thumb controls are rotated in the reverse direction (forks-first) from neutral:

•reverse travel signal is detected via hall effect sensors, converted into a travel. instruction in the ETAC, and transmitted via the CAN-bus to the power amplifier.

•the ETAC verifies that the emergency reverse button is not activated before supplying the travel command to the power amplifier.

•the ETAC verifies that switch S25 (Arm Angle B) is engaged for slow speed mode

•the ETAC verifies that both switch S24 (Arm Angle A) and switch S25 (Arm Angle B) are engaged for fast speed mode.

•the voltage at M– of the drive motor will vary from 24V to 1V. The voltage is proportional to the position of the thumb controls.

•the drive wheel starts to rotate in reverse direction at a speed proportional to the voltage at M–.

Emergency Reverse

If the emergency reverse button (belly button) is closed with the control handle lowered in travel mode, the control system provides an immediate, rapid acceleration in the reverse (forks-first) direction. The following occurs:

•the emergency reverse signal is converted into a reverse travel instruction and transmitted via the CAN-bus to the power amplifier.

•travel and speed inputs are ignored.

•the power amplifier provides maximum torque immediately after the emergency reverse button is activated.

•maximum reverse travel continues until the emergency reverse button is released.

Power Amplifier

The basic functions of the power amplifier includes:

•the direction control section that controls the drive motor direction by manipulating the drive motor field polarity according to the directional signal inputs from the ETAC.

•the speed control section that controls the drive motor speed and torque by monitoring the position change of the Arm Angle A and Arm Angle B switches. Variable motor speed is accomplished by separate control of field and armature currents.

•the emergency reverse circuitry in the ETAC which provides the directional travel control commands to the power amplifier.

•the control circuit section which controls all truck inputs and outputs (excluding handle head inputs).

Electronic Tiller Arm Card (ETAC)

The programmable motor control functions are performed by the electronic circuitry housed within the control handle [Electronic Tiller Arm Card (ETAC)]. The basic functions of the ETAC include:

•monitoring relative positioning of the thumb controls to eighteen hall effect sensors for speed and direction control

•monitoring the position of the emergency reverse button for emergency reversing of the truck direction

•monitoring truck performance and providing input data and commands to the service display

•providing lift/lower input commands to the power amplifier

•monitor horn switches S18-1 and S18-2 for horn operation

•monitoring and defining truck performance parameters

00700-CL340-05, Issued: 2 May 20053-7