Electronic Throttle Control(ETC) System

1. LECTURER NAME: MR. KHAIRUL AKMAL BIN NUSI HP. NO: 012-3458101 Electronic Throttle Control(ETC) System

2. HOW ELECTRONIC THROTTLE CONTROL WORKS • There are three basic components in electronic throttle control:- A position sensor on the accelerator pedal (actually there are 2 or 3 position sensors for redundancy).- An electronically-controlled throttle body with a small electric motor to open/close the throttle - A control module (the PCM or a separate ETC module that talks to the PCM via the CAN-bus or serial data link). • When the gas pedal is depressed, the electrical resistance of the potentiometers inside the pedal sensors change. The control module notes the change in position and assumes the driver wants to go faster. The module then looks at other sensor inputs (such as engine RPM, engine load via the MAP sensor, possibly even vehicle speed and which gear the transmission is in) and calculates how much throttle opening is needed. The module then sends a command to the electric motor on the throttle body to open the throttle a certain amount. A pair of throttle position sensors on the throttle shaft then note the change in throttle position and provide feedback signals to the control module so the module knows the exact position of the throttle and that everything is working correctly.

3. ELECTRONIC THROTTLE CONTROL FAILSAFE OPERATION • For redundancy backup and failsafe operation, the accelerator pedal usually has two or even three position sensors. In a 2005 Mustang, three sensors are used. Two decrease their resistance (increase voltage) when the pedal is depressed, and the third increases its resistance (decreases voltage). As long as the position sensor signals increase and decrease by the same amount (mirror each other), the circuit is assumed to be working correctly. • On most vehicles, an electronic throttle fault will put the system into a "limp-in" mode that will limit engine speed. On the Mustang, that means idle speed only. On a Corvette, the limit is a maximum vehicle speed of 30 mph. The throttle control system will remain in the limp-in mode until the fault can be diagnosed and repaired.

6. Typical System Configuration

7. Driving DC-Throttle-motors with additional air by pass valve • The main characteristic of a throttle valve, which is used tandem with a bypass valve, is the neutral position. In the idle mode it is completely closed with a strong spring and the air-bypass valve controls the idle speed. This means that the motor has only to drive the throttle in one direction. Therefore the electronic driving unit needs a half bridge or a single-switch together with a freewheeling diode. One standard PWM capable output pin of a microcontroller can be used for this task. Dead time generation is not required. The rated position of the throttle is given by an ETC potentiometer. A potentiometer is coupled with the gas pedal mechanics and gives a linear voltage signal as input to the ECU. • To generate a feedback signal, which is important for the control circuit, two potentiometers are connected internally to the throttle valve. They supply the ECU with two independent analog signals, in order to give information about the actual position of the throttle. Normally one signal decreases while the other signal increases. Both signals are proportional to the revolution angle of the system. In principle only one of these two position signals is necessary for the control circuit. But to improve the system accuracy, the second signal is used as an additional control value

8. Driving DC-Throttle-motors with additional air by pass valve • The throttle itself can also adjust the idle speed. Small air masses must be controlled precisely. Therefore it is necessary to drive the motor very exactly in both directions around the neutral position. This system requires power-stages in an H-bridge configuration to realize the bi-directional mode of the DC-motor. The capture compare unit of the microcontroller should support the functionality of full bridge driving.

9. Control of the idle speed only • Some throttles adjust only the idle speed with a motor, but the acceleration and driving of the engine is still done by a mechanical coupling to the acceleration pedal. As already mentioned Infineon Technologies has two products in the portfolio which support full bridge driving combined with some additional functionality. The devices can be controlled by PWM up to 2 kHz. • The functional modes (turn clockwise, turn counter clockwise and brake) are determined by the two input pins. Depending on the allowed power dissipation and the intended decay time the freewheeling can be done by switching over to the second path of the bridge, with the integrated diodes or with the brake-function, where both low side switches are turned on.

10. Driving the full range of a throttle with standard H-bridge • If the complete deflection of the throttle is done with the motor, like in chapter 1 described, standard H-bridges like the BTS780GP or the BTS7710GP can be used. They are suitable for big throttles with high currents. These bridges consist of a two channel smart power high side switch and two standard power-MOSFETs, which are protected by the high side switches against short of load and short circuit to ground. • The power-MOSFETs can be pulsed with very high frequencies, up to 100kHz. But the high side switches can not be switched faster than 1kHz. • Therefore they are not suitable to be switched on in the freewheeling phase of the motor (active freewheeling) at high frequencies. However, it is no problem to use the reverse diode of the high side switch as freewheeling diode. The special power package allows the bigger power losses caused by this kind of driving.

11. Driving with dedicated bridges for throttle control • Two new power-products on the roadmap, which are specially designed for ETC-Systems (TLE5209 and TLE6209). Similar to the TLE5205-2 family these devices consist of an H-bridge and are controlled by two input pins. However the new devices have a different input logic. One of the two pins is a direction control, and the other is an PWM-input. The first one, the direction pin, adjusts the different modes “forward” and “reverse”. • The moving speed of the throttle control system is given by the duty-cycle of the PWM signal on the second input pin. That way only one fast PWM-channel of the microcontroller is required. The TLE5209 is a low cost solution. It is designed for continuous currents up to 5A and peak currents of 7,5A at maximum which makes it suitable for small throttles or for throttle idle speed control.

12. The maximum PWM-frequency is 1 kHz. Internal monitoring functions protect the device against all possible faults. Two status pins allow an error diagnosis of the full-bridge. Figure 8 shows a block diagram of this device. If both inputs are on a high level, the bridge turns the current flow in the reverse direction. During this phase the motor is brake very strong. As a result, the decay time decreases compared to the normal braking phase, where only both high side switches are turned on.

14. Electronic throttle control (ETC) is an automobile technology which connects the accelerator pedal to the throttle, replacing a mechanical linkage. Most automobiles already use a throttle position sensor (TPS) to provide input to traction control, antilock brakes, fuel injection, and other systems, but use abowden cable to directly connect the pedal with the throttle. • An ETC-equipped vehicle has no such cable. Instead, the electronic control unit (ECU) determines the required throttle position by calculations from data measured by other sensors such as an accelerator pedal position sensor, engine speed sensor, vehicle speed sensor etc. The electric motor within the ETC is then driven to the required position via a closed-loop control algorithm within the ECU.

16. Control Module • There are so many different PCMs, accurate identification of the PCM and its correct replacement is absolutely essential to prevent unnecessary returns. Accurately identifying the PCM requires not only the vehicle year, make, model and engine size, but also the OEM part number on the PCM itself. Most supplier catalogs list replacement PCMs both ways. Many PCMs appear to be exactly the same on the outside (same sized box and connectors) but may be wired or calibrated differently inside. • The wrong PCM is installed in a vehicle, it may run but probably will not run well. Close enough is not good enough when it comes to replacing PCMs. It must be the correct replacement to work right. Always refer to the OEM number on the PCM and look it up in the suppliers cross reference index to find the right part. On some occasions, after the new PCM is installed, it requires a "flash" operation, to "adapt it" specifically to the vehicle it is installed in.

17. Throttle Actuator • Throttle Actuator is designed to provide remote control of an engine throttle in conjunction with a Froude Hofmann controller. The actuator comprises of a brushless DC servomotor, driving a linear precision ball screw. A flexible cable is supplied for the connection between the actuator and engine throttle. Alternatively a customer supplied direct linkage may be used.

19. Throttle-By-Wire • Throttle-By-Wire, which is the same as Electronic Throttle Control (ETC), or "Throttle Actuator Control" (TAC), is replacing the throttle linkage on more and more late model vehicles. The mechanical linkage or cable between the accelerator pedal and throttle body has been replaced with a gas pedal position sensor and an electronically-operated throttle. • Throttle-By-Wire eliminates the sticking and binding problems that sometimes occur with mechanical linkages, and eturn spring failures that may prevent the throttle from closing (a runaway engine). Throtle-By-Wire also helps reduce emissions and improves fuel economy. But the main advantage is that Throttle-By-Wire allows the engine computer to integrate torque management with cruise control, traction control and stability control.

20. With cruise control, integrating throttle control into the engine management system eliminates the need for external vacuum servos or motors to maintain a constant vehicle speed. It also makes "adaptive" cruise control possible (with some additional sensors) so a vehicle can match the speed of the vehicle ahead of it and maintain a safe following distance. • Throttle-By-Wire also provides some warranty advantages for the vehicle manufacturer, too, by limiting "abusive driving" by lead-footed motorists. If you put the pedal to the metal on a car with Throttle-By-Wire, you won't impress anybody by smoking the tires. It won't happen -- unless there is an over-ride switch to deactivate traction control. Even then, the computer may limit engine torque to certain limits to protect the transmission and drivetrain from possible damage.

21. THROTTLE-BY-WIRE FAILSAFE OPERATION • For redundancy backup and failsafe operation, the accelerator pedal usually has two or even three position sensors. In a 2005 Mustang, three sensors are used. Two decrease their resistance (increase voltage) when the pedal is depressed, and the third increases its resistance (decreases voltage). As long as the position sensor signals increase and decrease by the same amount (mirror each other), the circuit is assumed to be working correctly. But if any of the position signals disagree, it indicates a fault and the module sets a code and turns on the Malfunction Indicator Lamp (MIL). On the Mustang, an electronic throtttleconrol fault will also illuminate a little yellow wrench warning light.

22. THROTTLE-BY-WIRE DIAGNOSTICS • Most of the faults that occurr in a Throttle-By-Wire control systems are things you would expect, like pedal or throttle position sensors that wear out and skip or produce erratic signals, motor failures in the throttle body, and electrical problems like loose or corroded wiring connectors. • A code reader or scan tool is required for diagnostics. Generic OBD II trouble codes for possible pedal position sensor faults include P0120 through P0124, P0220 through P0229, plus any OEM enhanced P1 or P2 series codes for that specific vehicle. • If a fault occurs in the motor on the throttle body, it will be detected by the feedback signals from the throttle position sensors. Generic OBD II codes for this kind of problem include P0638 & P0639, plus any OEM enhanced P1 or P2 series codes for that specific vehicle.

23. Throttle-By-Wire Service Precautions • On some systems, a special relearn procedure is required when parts have been replaced or the throttle control wiring harness has been disconnected. The relearn procedure is necessary so the control module can learn the rest positions of the gas pedal and throttle. On some vehicles this occurs automatically every time the key is turned on. But on others it requires a scan tool or special manual procedure. Refer to the OEM service literature for specific instructions.