AP-1055D and BG-2455D Asphalt Pavers Propel System Caterpillar

Illustration 1	g01166248

Propel Control Circuit

Note: The electrical system on this machine is wired according to the Caterpillar corporate wiring system. This system requires every wire to be labelled with a specific color and a specific number. Each color and each number has a specific meaning.

The color of the wires have the following meaning:

• Red wires are positive.

• Black wires are negative.

• Orange wires are in starting circuits.

The wire numbers have the following meaning:

• 100 wires are power circuits.

• 200 wires are ground.

• 300 wires are the basic machine circuits.

• 400 wires are monitoring circuits.

• 500 wires are accessory circuits.

• 600 wires are lighting circuits.

• 700 to 999 wires are control circuits.

Control Functions

The control functions of the machine ECM for the propel system can be divided into the following eight categories:

• Neutral start control

• Selection of the operator station

• Closed loop speed control

• Closed loop steering control

• Open loop speed control and open loop steering control

• Direction and backup alarm control

• Gear control

• Brake control

Note: The machine ECM discontinues the output signals to the electric displacement control valves and the output signal to the parking brake solenoid if a short to the battery or ground is detected certain circuits. Consequently, the propel pumps will not generate flow. The parking brakes will be engaged. The machine will not move.

The machine ECM discontinues the output signals to the electric displacement control valve's and the output signal to the parking brake solenoid if a short to the battery or ground is detected in one of the following circuits:

• The steering sensor circuit

• The propel speed dial circuit

• The propel lever sensor circuit

• The decelerator sensor circuit

Power Distribution

The machine ECM receives power from the circuit breaker for the machine ECM at the following terminals:

• "J2-1"

• "J2-23"

• "J2-47"

The machine ECM is grounded at the following terminals:

• "J2-2"

• "J2-22"

• "J2-46"

The lines for the Cat Data Link are connected at terminals "J1-7" and "J1-8".

The line for the Cat Data Link allows information to flow between the following components:

• Machine ECM

• The Caterpillar Monitoring System

• The external service tools

The lines for the CAN Bus allow the machine ECM to transfer information to the engine ECM.

The lines for the CAN Bus are connected to the following terminals:

• "J1-6"

• "J1-18"

The following terminals are common return lines from components in the propel system:

• "J1-12"

• "J2-13"

• "J2-36"

• "J2-52"

Terminal "J1-11" is the power supply to the sensors in the circuit. In order to control the propulsion of the machine, the machine ECM uses the remaining terminals to analyze input signals. The remaining terminals are also used to generate output signals.

The following components receive power from the circuit breaker for the propel system:

• The left parking brake switch

• The right parking brake switch

• The left operator station status indicator

• The right operator station status indicator

• The operator station selector switch

Selection of Operator Station

The machine ECM monitors the circuits at terminals "J2-30" and "J2- 31" in order to determine the position of the operator station selector switch. When the operator station selector switch is in the RIGHT position, the circuit at terminal "J2-30" is complete. When the switch is in the LEFT position, the circuit at terminal "J2-31" is complete.

The machine ECM analyzes the input from the operator station selector switch in order to control the number one operator station relay and the number two operator station relay. The condition of these relays determines whether the propel controls at the left control station provide the input to the machine ECM or the propel controls at the right control station provide the input to the machine ECM.

When the operator station selector switch is in the LEFT position, the machine ECM does not energize the coils of the number one operator station relay and the number two operator station relay. The power from terminal "J1-11" from the machine ECM flows across contacts 30 and 87a from the number one operator station relay.

This power is available at the following components:

• The left steering sensor

• The left propel speed dial

• The left decelerator sensor

• The left propel lever sensor

When the number two operator station relayis de-energized, a ground path is created for the left propel mode switch.

When the operator station selector switch is in the RIGHT position, the machine ECM generates an output signal from terminal "J2-14" to the coils of the number one operator station relay and the number two operator station relay.

In this situation, the following components receive power from terminal "J1-11" of the machine ECM:

• The right steering sensor

• The right propel speed dial

• The right decelerator sensor

• The right propel lever sensor

This power flows to these components across contacts 30 and 87 of the number one operator station relay. A ground path for the rightpropel mode switch is created across contacts 30 and 87 of the number two operator station relay.

Neutral Start Control

The machine ECM applies the neutral start logic under the following conditions:

• The input signal from the active propel lever sensor indicates that the propel lever is not in the NEUTRAL position. The input signal from the active propel lever sensor is at terminal "J1-24".

• The engine speed input indicates that the engine is not running. The machine ECM applies the neutral start logic. The engine speed input is sent from the engine ECM through the lines for the CAN Bus.

By using the neutral start logic, the machine ECM prevents the machine from moving when the engine is started. This is regardless of the position of the propel lever.

When the engine is started with the propel lever out of the NEUTRAL position, the ECM does not generate output signals to the electric displacement control valves or to the parking brake solenoid. Therefore, the propel pumps cannot generate flow, and the parking brakes are engaged. The machine ECM will not allow the machine to move until the propel lever is moved into the NEUTRAL position and then out of the NEUTRAL position.

Closed Loop Speed Control

During normal straight travel operation, the machine ECM controls the machine speed by using the closed loop speed control logic which is programmed into the software.

When this logic is used, the machine ECM monitors input from the following components:

• The left track speed sensor

• The right track speed sensor

• The engine ECM (engine speed input)

• The Caterpillar Monitoring System (harness code input)

• The active propel speed dial

• The propel lever sensor

• The decelerator sensor

• The propel mode switch

• The parking brake switch

The machine ECM uses the information that is listed above in order to determine the target speed for the machine.

The machine ECM uses the harness code input from the Caterpillar Monitoring System in order to determine the model of the machine. The harness code input is transferred through the lines for the Cat Data Link. After the machine model has been identified, the machine ECM can apply the appropriate machine control logic.

The machine ECM simultaneously analyzes signals from all of the input devices.

The machine ECM does not generate an output signal to any of the electric displacement control valves if the analysis indicates that the machine should not be moving.

The following conditions are examples of a condition that will prevent the machine from moving:

• The parking brake switch is in the ON position.

• The decelerator pedal engaged.

• The propel lever is in the NEUTRAL position.

If the analysis indicates that the machine should be moving, the machine ECM controls the operating speed and the direction of the machine. The machine ECM will generate a output signal (mA). This signal is a pulse width modulated signal.

This signal is sent to the forward electric displacement control valve or the reverse electric displacement control valves.

This signal is generated at the following terminals:

• "J2-62" (forward)

• "J2-64" (forward)

• "J2-63" (reverse)

• "J2-65" (reverse)

The machine ECM must determine the appropriate output signal that is needed to be sent to the electric displacement control valves. This is used to establish the target machine speed.

In order to determine this signal, the machine ECM analyzes input from the following components:

• The active propel speed dial

• The propel lever sensor

• The decelerator sensor

• The engine ECM (engine rpm)

The following components receive power from terminal "J1-11" across the number one operator station relay:

• The propel speed dials

• The propel lever sensors

• The decelerator sensors

These components are grounded at terminal "J1-12" of the machine ECM. These components send pulse width modulated signals to the machine ECM.

Note: The propel speed dials and the propel lever sensors are connected to pulse width modulated buffers which generate the pulse width modulated signals.

The active buffer for the propel speed dial sends a pulse width modulated signal to terminal "J1-14" of the machine ECM. The duty cycle of the signal is proportional to the position of the active propel speed dial. The active buffer for the propel lever sensor sends a pulse width modulated signal to terminal "J1-24" of the machine ECM. The duty cycle of this signal is proportional to the position of the active propel lever. The active decelerator sensor sends a pulse width modulated signal to terminal "J1-2" of the ECM. The duty cycle of the signal is proportional to the position of the active decelerator pedal.

The machine ECM uses the input at terminal "J1-24" in order to determine the desired speed and direction of travel. The machine ECM analyzes the signal at terminal "J1-24". Then, the machine ECM determines the position of the active propel lever. The lowest duty cycle corresponds to the FULL REVERSE position of the propel lever. The highest duty cycle corresponds to the FULL FORWARD position of the propel lever. The duty cycle which corresponds to the NEUTRAL position of the propel lever is in the center of the range.

A signal will not be sent to the electric displacement control valves if the propel lever is in the NEUTRAL position. As the input signal at terminal "J1-24" decreases from the neutral value, the machine ECM increases the signal which is sent from terminals "J2- 63" and "J2-65" to the right and left reverse electric displacement control valves. As the input signal at terminal "J1-24" increases from the neutral value, the machine ECM increases the signal which is sent from terminals "J2-62" and "J2- 64" to the right and left forward electric displacement control valves.

The machine ECM controls the maximum travel speed of the machine when the active propel lever is in the FULL SPEED position. The machine ECM uses the information that is sent to the input at terminal "J1-14". When the active propel speed dial is in the MINIMUM SPEED position, the machine ECM directs the minimum signal to the corresponding electric displacement control valve. The machine will not move even when the propel lever is in FULL SPEED. As you move the propel speed dial toward the FAST position, the machine ECM will increase the duty cycle of the signal. This signal is sent to the corresponding electric displacement control valve. Ultimately, as the speed dial is moved closer to the FULL SPEED position, maximum travel speed increases. Incremental movements of the propel lever cause larger increases in travel speed.

The machine ECM monitors the input signal at terminal "J1-2" in order to determine the position of the active decelerator pedal. As the decelerator pedal is depressed, the duty cycle of the signal at terminal "J1-2" decreases. As the duty cycle decreases, the machine ECM decreases the signal which is sent to the corresponding electric displacement control valve. As a result, the travel speed decreases. When the decelerator pedal is fully depressed, the machine ECM discontinues the signal to the electric displacement control valve. Movement of the decelerator pedal causes the same basic effect as movement of the propel lever.

The left and right track speed sensors receive power directly from terminal "J1-11" of the machine ECM. The sensors are grounded at terminal "J1-12". These sensors send square wave frequency signals to the machine ECM. Each sensor sends two signals to the ECM, a primary signal and a secondary signal. The signal frequency is proportional to the speed of the corresponding track. The left track speed sensor sends the primary signal to terminal "J1-25" of the machine ECM and the secondary signal to terminal "J1-15". The right track speed sensor sends the primary signal to terminal "J1-3" of the machine ECM and the secondary signal to terminal "J1-26".

If the primary signal does not agree with the secondary signal, or the input from the right and left speed sensors is not equal, the machine ECM will log a fault.

The machine ECM will then control the machine speed with open loop logic for speed and steering control. See the following paragraph below.

The machine ECM analyzes the input signals from the speed sensors. The machine ECM then compares the input signals to an actual machine speed.

To determine whether the actual speed matches the desired speed, the machine ECM must determine the position of the following:

• The active propel lever

• The propel speed dial

• The decelerator pedal

• The propel mode switch

The machine ECM then compares this information to the actual machine speed.

The machine ECM monitors the circuits at terminals "J1-54" and "J1- 55" in order to determine the position of the active propel mode switch.

The circuit at terminal "J1-54" is closed in the following conditions:

• The propel mode switch is in the TRAVEL position.

• The circuit at terminal "J1-55" is closed.

• The switch is in the MANEUVER position.

When the switch is in the PAVE position, the circuits at terminals "J1-54" and "J1-55" are both open.

In straight travel, the machine ECM matches the speed of both tracks by monitoring the speed sensors and by adjusting output to the electric displacement control valves.

Closed Loop Steering Control

During normal steering operation, the machine ECM controls the machine speed by following the logic that is used in the closed loop steering control. This logic is programmed into the software. When this logic is used, the machine ECM monitors the same components that are monitored during normal straight travel operation. In addition, the machine ECM monitors the active steering sensor.

The input from the active steering sensor allows the machine ECM to calculate the speed differential which is required to maintain the relative speed of the right and left tracks during turns. As a result, the closed loop steering control allows the machine ECM to act as an "electronic differential".

The steering sensors receive power from terminal "J1-11" of the machine ECM. This is across the number one operator station relay. These sensors are grounded at terminal "J1-12" of the machine ECM. The active sensor sends a pulse width modulated signal to terminal "J1- 16" of the machine ECM. The duty cycle of the signal is proportional to the rotational angle of the steering wheel.

The machine ECM analyzes the signal at terminal "J1-16". The machine ECM then determines the position of the steering wheel. The lowest duty cycle corresponds to the FULL LEFT position of the steering wheel. The highest duty cycle corresponds to the FULL RIGHT position. The duty cycle which corresponds to the STRAIGHT TRAVEL position of the steering wheel is in the center of the range.

When the machine ECM detects that the active steering wheel is in the STRAIGHT TRAVEL position, the closed loop steering control is not active. When the operator moves the active steering wheel in either direction, terminal "J1-16" of the machine ECM detects the change in the steering wheel. The machine ECM will calculate the speed differential between the tracks that must be maintained, in order to sustain the desired machine speed through the turn.

The machine ECM then modifies the pulse width modulated output signals which are sent from the following terminals:

• "J2-62" (forward)

• "J2-64" (forward)

• "J2-63" (reverse)

• "J2-65" (reverse)

Under certain operating condition, the tracks can be counterrotated.

The machine ECM simultaneously sends output signals to the right or the left forward electric displacement control valve and the machine ECM simultaneously sends output signals to the left or the right reverse electric displacement control valve in the following conditions:

• The active machine speed dial is in the MINIMUM SPEED position.

• The active propel mode switch is in the MANEUVER position.

• The active steering wheel is turned to the right or to the left.

Open Loop Speed Control and Open Loop Steering Control

If a fault is detected in the left or in the right track speed sensor, the machine ECM uses the logic that is in the open loop steering control and the open loop speed control in order to control the machine.

When this logic is used, the machine ECM monitors input from the following components:

• The active steering sensor

• The propel speed dial

• The propel lever sensor

• The decelerator sensor

• The propel mode switch

• The parking brake switch

• The engine ECM (engine speed input)

• The Caterpillar Monitoring System (harness code input)

The machine ECM uses the harness code input in order to determine the target speed for the machine.

The machine ECM generates output signals which are pulse width modulated at one of the combinations of the following terminals:

• "J2-62" and "J2-64"

• "J2-63" and "J2-65"

The signals are sent to the forward or the reverse electric displacement control valve.

Through these signals, the machine ECM controls the following:

• The operating speed

• The travel direction

• The turning radius of the machine

Since the left and the right speed sensors do not provide input to the machine ECM when the open loop speed control and the open loop steering control is used, the desired machine speed and/or actual machine speeds cannot be controlled. As a result, the machine may not track straight and/or the machine may exhibit erratic steering. The travel speeds will be limited to 50 percent of the maximum travel speed. The pave speeds will be limited to 50 percent of the maximum pave speed.

Direction and Backup Alarm Control

In order to determine the target travel direction, the machine ECM monitors the input which comes to terminal "J1-24" from the active propel lever sensor. None of the electric displacement control valves are energized when the propel lever is in the NEUTRAL position. As a result, the machine will not move. When the propel lever is out of the NEUTRAL position, an output signal is directed to the appropriate electric displacement control valve. If the propel lever is in the REVERSE range, the machine ECM also directs a signal from terminal "J2-24" to the backup alarm. The signal causes the backup alarm to sound.

Speed Control

The machine ECM monitors the input at terminals "J1-54" and "J1-55" in order to determine the position of the active propel mode switch. The machine ECM monitors the input at terminal "J1-24" in order to determine the position of the active propel lever. When the active propel mode switch is in PAVE position, the switch is open. The circuits at terminals "J1-54" and "J1-55" of the machine ECM are also open. When the propel mode switch is moved to the TRAVEL position, contacts 1 and 2 close. This completes the circuit at terminal "J1-55" of the machine ECM. When the propel mode switch is moved to the MANEUVER position, contacts 2 and 3 of the switch close. This completes the circuit at terminal "J1-54" of the machine ECM.

The machine ECM does not direct an output signal from terminal "J2-45" to the shift solenoid in the following conditions:

• The circuits at terminals "J1-54" and "J1-55" are both open (PAVE position).

• The circuit at terminal "J1-54" is closed (MANEUVER position).

When a closed circuit is detected at terminal "J1- 55" and an open circuit is detected at terminal "J1-54", the machine ECM directs an output signal from terminal "J2-45" to the shift solenoid.

The active propel lever must be in the NEUTRAL position in order for the machine ECM to change the status of the shift solenoid. If the propel lever is not in the NEUTRAL position, the machine ECM will not allow a shift until the propel lever has been cycled into NEUTRAL.

Brake Control

The machine ECM monitors the following components in order to determine if the machine should be stopped:

• The active parking brake switch

• The propel speed dial sensor

• The propel lever sensor

• The decelerator sensor

• The engine ECM (engine speed input)

Conditions which indicate that the machine should be stopped include the following conditions:

• Active parking brake switch in the ON position

• Active propel speed dial at MINIMUM speed

• Active propel lever in the NEUTRAL position

• Active decelerator pedal that is fully depressed

• The engine speed is calculated at zero revolutions per minute.

If the machine ECM detects any combination of the above conditions, the ECM discontinues the output signals to the electric displacement control valves and to the parking brake. As a result, the propel pumps cannot generate flow, and the springs in the parking brakes engage the brakes.

Propel Override Circuit

Illustration 2	g01166262

If the machine ECM detects a fault which prevents the machine from moving or if the computer is faulty, the propel override switchescan be used to bypass the machine ECM so that the machine can be moved. The left and right tracks can be controlled independently.

In order to activate the propel override function, the override harness must be connected to the plug. When the override harness is connected, the machine ECM will not interpret the machine movement which is caused by the override switches as unwanted movement.

Power Distribution

Power flows through the 122-BU wire from the circuit breaker for the propel system. Power flows from the circuit breaker for the propel system to contact 5 of the left and right propel override switches. The 122-BU wire also transfers power to two resistors and to contact 1 of the connector for the override harness. On the downstream side of the resistors, reduced power is available to contact 2 of the left propel override switch, through the A340-YL wire. Reduced power is also available to contact 2 of the right propel override switch, through the A327-WH wire.

Note: The resistors in the circuits to contact 2 of the propel override switches protect the coils for the electric displacement control valves from overvoltage when the propel override switches are used.

Reverse Operation

When the left propel override switch is in the REVERSE position, power transfers across contacts 2 and 3 of the switch and to the left reverse electric displacement control valve. Also, power transfers across contacts 5 and 6 of the left switch to the parking brake solenoid. The left reverse electric displacement control valve and the parking brake solenoid energize, and the left track moves in reverse.

When the right propel override switch is in the REVERSE position, contacts 2 and 3 and contacts 5 and 6 of the switch are closed. Power transfers to the right reverse electric displacement control valve, and power transfers to the parking brake solenoid. The right track then travels in reverse.

Forward Operation

When the propel override switches are in the FORWARD position, the forward electric displacement control valves are energized and the parking brake solenoid is energized. The machine will move forward. If one of the override switches is in the FORWARD position and the other override switch is in the REVERSE position, the tracks will counterrotate.