Section 8. Theory of Operation Traction System
Traction System Pre-Operational Checks (SelfTest) Before the truck can be operational, the VM performs the following checks: •
Seat switch (SW2) - CLOSED (operator seated)
•
Battery Interlock switch (SW30) (optional) - CLOSED
•
Parking Brake switch (SW7) - OPEN (parking brake released)
If truck is equipped with a Hand Direction Lever, the lever must be in the neutral position.
Travel After SelfTest is complete and no codes are displayed on the Operator Display, travel is allowed. Travel can be requested via one of two configurations. Standard configurations utilize a hand activated direction lever located on the steering column. The lever is moved forward (toward the mast) for forward travel and back (away from the mast) for reverse travel. It is used in conjunction with a single foot activated travel pedal located on the floor of the operator compartment to the right of the brake pedal. Travel speed is based on how far the pedal is depressed. The further down the pedal is depressed, the faster the truck travels. An optional configuration utilizes two pedals located on the floor of the operator compartment, to the right of the brake pedal. The left pedal is depressed for forward travel and the right pedal for reverse travel. Travel speed is based on how far either pedal is depressed. The further down the pedal is depressed, the faster the truck travels. NOTE: For two-pedal configuration, a jumper must be installed between J33-4 and J33-5.
8-6
Model 4700 Maintenance Manual Pre-Operational Checks (SelfTest)
Hand Direction Lever Moving the lever from the neutral position toward the mast closes Forward switch (SW9). Moving the lever from the neutral position away from the mast closes Reverse switch (SW10). These directional inputs are sent to the VM. The VM monitors the Enable switch (SW8) and the Travel Pot (P2). When the operator pedal is depressed, the Enable switch (SW8) closes. This informs the VM to recognize the Hand Direction Lever switch (SW9 or SW10) inputs. Output voltage from Travel Pot (P2) is compared to the previously Learned value and the VM converts the voltage value into a percentage-of-request. The VM converts travel direction and the percentage of the request into a message that is sent via the CAN-Bus to the Traction Power Amplifier (TPA) and Operator Display (OD). The TPA sends the RPM request to the Traction Motor(s) to satisfy the direction and speed request received by the VM. The TPA monitors the Encoder(s) (EN1 for single traction motor trucks; EN1 and EN2 for dual traction motor trucks) to verify that actual travel direction and speed matches what was requested. The VM constantly monitors the travel request and updates the information to the TPA as changes occur. All operational parameters that affect motor torque and speed are controlled by the TPA. The TPA also monitors the Temperature switch(es) (TS1 for single traction motor trucks; TS1 and TS2 for dual traction motor trucks). The temperature switch(es) are normally closed. They open when an overtemperature condition exists in the motor, causing a reduction in travel speed to allow the motor to cool. An icon on the Operator Display is also illuminated to alert the operator.
Two Pedal Configuration The Forward and Reverse travel direction pedals are located to the right of the brake pedal on the operator compartment floor. The left pedal is depressed for forward travel and the right pedal for reverse travel. When either pedal is depressed, the corresponding Forward switch (SW4) or Reverse switch (SW5) closes, sending an input to the VM as a request for forward or reverse travel. The VM monitors the Travel Pot (P2). Output voltage from P2 is
Publication 1160093, Issued: 20 May 2013
