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CAN bus based controller design for automatic clutch

In Electronic Infomation Category: C | on April 23,2011

Abstract: The design of a CAN bus based on automatic clutch controller, using high-performance microprocessor XC878 controller hardware and M5280FP datasheet and software development to complete the clutch. Design of the clutch motor drive circuit and M5280FP price and the implementation of automated clutch control procedures. Coordinated control for the clutch and M5280FP suppliers and the engine needs to design a CAN bus node interface circuit and a simple, practical and efficient CAN bus communication protocol.

Tests show that the design of the automatic clutch controller functions to meet the needs of practical applications, CAN communication module to send and receive data accuracy and high reliability.

As society develops, people on the cars comfort and safety have become increasingly demanding, and because of the heavy vehicle manual shift and clutch operation selection increased driving difficulty. For novice drivers, easy to turn off start ramp will be produced, fuel consumption and large, the clutch wear serious problems [1]. While driving automatic transmission car is simple, but its high cost, development difficult. This design of electronically controlled automatic clutch ACS (Automatic Clutch System) is based on the manual transmission installed in the electronic control system, cancel the clutch pedal, automated clutch. ACSs advantages are clear: Compared with the manual transmission, the driving control of more simple, with quick acceleration, driving comfort features; compared with the automatic transmission vehicles, ACS has a low cost, easy maintenance, economic, fuel-efficient.

1 system features

ACS modern electronic control technology for the control of dry friction clutch to simulate the drivers control action and good sense, to achieve the best combination of regular clutch, and its essence is for the car driver with a clutch of robot control, automatic clutch function. ACS controller designed in this paper several key functions to achieve the following.

(1) shift clutch: the controller receives the shift signal, the rapid automatic separation clutch, shift with auto clutch in place, combined with regular basis by the electronic control unit to determine vehicle driving cycle.

(2) Hill-start: the driver brake pedal, start the engine, the gearshift lever placed in a file or a reverse gear, release the hand brake, lift the brake is not pressed the accelerator after the car automatically slow driving, a smooth start, the impact is small, does not stall.

(3) turn off protection: motor cars and the course, speed and engine speed below the set value is automatically separated after the clutch, speed and engine speed higher than the set value, the clutch and then automatically combined.

(4) CAN communication: ACS controller via CAN bus interface for data communication with the engine controller for coordinated control of the clutch and engine to provide data support.

2 Hardware Design

2.1 controller component

Automatic clutch controller block diagram shown in Figure 1. Infineon microprocessor of the system used high-performance 8-bit microprocessor XC878CM, maximum operating frequency of 27 MHz, the chip hardware resources are very rich, on-chip integrated MultiCAN controller, capture / compare unit 6 ( CCU6), high-performance ADC module. XC878CM excellent performance to fully meet the systems design needs. The hardware of this system include power modules, data acquisition module, CAN communication module, the implementation of the motor drive module.

automatic clutch controller Figure 1 Schematic

(1) power module vehicle control system through the 12 V low voltage battery power supply, 8-bit MCU with 5 V power supply. Therefore, this system needs to use the power chip voltage conversion and isolation. The system selected Infineon power chip, TLE4290, the chip can provide stable voltage of 5 V, the error is within 2%, the input voltage up to 42 V. Tested and reliable of its work to meet the system requirements.

(2) CAN communication module using CAN communication module MultiCAN XC878CM chip CAN controller and transceiver IFX1050G Infineon as a high-speed CAN communication hardware. CAN module is responsible for the clutch between the controller and the engine controller, data exchange and sharing, the coordination of the engine and clutch control to provide data communications support.

(3) the implementation of the motor drive module used in the implementation of this system, the motor is rated at 12V DC motor. IO ports using a single chip implementation of the motor rotation direction control, PWM output control all the way to the motor speed.

PWM wave by a single chip containing the CCU6 module is configured to generate comparative models. Microcontroller by Infineon chip BTS7810K motor drive to achieve the implementation of motor control.

(4) data acquisition module of the system of data collection are three types: digital, analog, frequency content. Switch pointing mainly linked to the fire signal and the driver file signals through the microcontroller I / O ports collection.

XC878CM-chip microcontroller with 8 analog inputs, a choice of high-performance 10 bit ADC, analog can be easily used for acquisition. XC878CM CCU6 included work in the module can be configured to capture mode, the speed sensor for collecting the amount of signal sent to the frequency. As the environment interfere with the larger car, the signal acquisition circuit need to add filtering, voltage conditioning and other circuits. In addition, the amount collected for the frequency, because the reception is a pulse signal, also need to use a Schmitt trigger for pulse shaping.

2.2 motor drive circuit design

Clutch actuator 12 V DC motor driven by the microcontroller using pulse width modulation PWM technique to control the motor speed. PWM speed control method to control a simple, effective dynamic response, wide speed range applications the advantages of a very wide range of speed control methods.

The direction of rotation of DC motor control need to build a H bridge circuit, the self-built H-bridge circuit and gate drive circuits are often difficult to ensure reliability. Therefore, we selected the integrated motor driver chip to drive the clutch BTS7810K perform motor. Chip BTS7810K is a full bridge motor driver chip, which integrates a H bridge motor drive circuit and gate drive circuit, the operating frequency of up to 1 kHz or more, can be easily and reliably achieve the DC motor control. BTS7810K normal operating mode of the input and output characteristics shown in Table 1.

Table 1 BTS7810K input and output properties

Motor drive circuit shown in Figure 2, the microcontroller using an I / O port output control motor rotation, all the way to control the motor speed PWM output. Two control signals with the doors and through a gate composed of two non-interface circuit connected to the driver IC input IH1, IH2. This is to ensure that both the two inputs is not high, straight leg to prevent problems, improve system security and reliability.

Figure 2 Motor Drive Circuit

2.3 CAN Node Interface Design

CAN bus is a German company Bosch 90 in the early 20th century to solve a number of Hyundai Motor control and test equipment in the exchange of information between the developed a serial communication protocol network [3]. It has a high transmission speed, reliability and real-time characteristics of a good, fits well with ACS and coordinated control of the communication needs of the engine. On the integrated control of engine and clutch, full use of electronic engine control system controls engine speed and timely, accurate and features, so that coordination with the clutch, the clutch will help achieve better control performance, and to improve shift quality.

CAN node hardware circuit includes: a microcontroller with CAN controller for data sent and received CAN transceiver. This selected with the on-chip microprocessor XC878CM CAN controller, CAN is responsible for initialization and data processing. MultiCAN module addition to transceivers with integrated CAN bus controller for all functions. In addition, MultiCAN also has advanced the acceptance filtering, advanced data management, advanced interrupt management, and other fine features. Many different types of CAN transceiver, this design chosen Infineons high-speed transceiver IFX1050G. CAN node interface circuit diagram shown in Figure 3.

Figure 3 CAN node interface circuit diagram

3 Software Design

Electronic control unit ECU of the control software mainly by the clutch control procedures and CAN bus communication components.

3.1 clutch control software design

Clutch control program consists of three parts: clutch control procedures, starting with control procedures, shifting with control procedures. Separation of control procedures which is relatively simple, ECU have been isolated instruction, full separation of the clutch, and accurately you can stop at the point of complete separation. Difficulty lies in the control of the clutch start with control. Clutch start with the vehicle starting process is to ensure a smooth, comfortable, start does not stall, but also to ensure the rapid start, reducing the generation of friction work, to extend clutch life. Therefore, to obtain better control effect in addition to the binding capacity of the clutch control, but also with the speed of the clutch control, and coordination with the engine control and improve the control effect. Figure 4 shows the flow chart starting with the control software. Shifting control of the process and start with the clutch control in the control strategy is similar to not repeat them here.

Figure 4 starting with the control software flow chart

3.2 CAN Communication Protocol

CAN communication protocol, including the physical layer, data link layer and application layer. Physical layer and data link layer is implemented by hardware in the use of CAN communication, the need for developers to define their own application layer protocol. Structural application layer protocols main task is assigned ID defined message cycle, determine the mapping between signals and messages. Design of the main factors to consider real-time data transfer requirements of the relative importance of the data, applications and data related to the time control algorithms on the data requirements. There are some existing international standards, such as CANopen, SAE J1939 and so on.

Some use of a simple communication protocol to meet the requirements of the circumstances, the use of complex protocols will be a waste of resources, the user will feel in the application of inconvenience, but to restrict flexibility. CAN bus network designed in this paper, only the clutch controller and engine controller two nodes. Only two nodes for the experimental platform, this amount of code from the protocol, the target information system, software development cost perspective, to define a simple and reliable CAN protocol. Specific communication protocol as defined in Table 2, the identifier used to indicate the priority of the information, the smaller the higher the priority identifier.

Table 2 CAN bus communication protocol

4 CAN communication test test This experiment is in itself

clutch simulation platform built on the. The experimental platform is a clutch control panel, the accelerator pedal, brake pedal, related sensors, actuators and engine simulation clutch control board composition. Simulation of the clutch and the engine control board through the CAN bus communication between the control board. Figure 5 shows the course of the experiment through the CAN bus transmission gear change information, Figure 6 CAN bus passed through the accelerator pedal opening signal.

Figure 5 stalls information

Figure 6, the opening of the accelerator pedal signal

This paper presents a set of electronically controlled automatic clutch control programs, and make the system hardware and software development, the initial realization of the basic functions of the automatic clutch designed CAN bus interface. In the experimental platform to validate the control scheme and the CAN communication module of the feasibility and reliability, lay the foundation for the road test.

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