The measurement block incorporating the system for condi-tioning four analogue signals enables the gain and offset control, so the sensors operating in the voltage range ±10 V can be easily connected to the ACS. The voltage range handled by the meas-urement block necessitates the use of a DC/DC +5 V/±15 V con-verter in the power supply block. The MSP430 has an integrated USB interface which can be utilised for programming and data exchange with the microprocessor. The current levels to be han-

 Unauthenticated

Download Date | 3/31/16 1:19 PM 

Maciej Rosół, Bogdan Sapiński

Autonomous Control System for a Squeeze Mode MR Vibration Isolator in an Automotive Engine Mount

 dled by the USB interface block are limited to 100 mA and the data lines D+ and D- are surge-voltage protected.

The CAN bus block enables the ACS communication with pe-ripheral devices via the CAN bus. This block is implemented

 on an integrated SPI/CAN converter and a CAN transceiver. The maximal data transmission throughput is 1 Mbit/s.

Fig. 1. Block diagram of the ACS

Tab. 1. Technical parameters of MSP430

Parameter Description

Program memory 128 kB

Data memory SRAM 8+2 kB (additional 2 kB without

I/O number Max. 63

Number of Timers/Counters 4 Watchdog Yes

PWM mode Yes

Communication protocols (USCI) Channel A: UART/LIN/IrDA/SPI

Channel B: I2C/SPI

DMA 3 channels

Multiply unit (MPY) 3232

Comparator Yes

Integrated temperaturę sensor Yes

A/D converter 12 channels, 12-bit

Integrated USB interface Yes

3. TESTING

3.1. Laboratory setup

The schematic diagram of the laboratory set-up for ACS test-ing is shown in Fig. 2. The power interface and ACS are supplied from the battery +12 V. The monitoring and data acquisition are supported by a purpose-developed application written in the Lab-View and activated on a PC. The data transmission between the ACS and PC is effected via a sbRIO-9639 card equipped with the CAN interface (ACS connection) and the Ethernet (PC con-nection). The power interface ensures the current levels 11−12 A to be as required in the electromagnet coil.

Fig. 2. Block diagram of the test configuration

The application supporting the operation of measurement sensors and control of the electromagnet coil is MSP430 enabled. The primary function of this application, written in the C/C++ language in the Code Composer Studio (CCS) environment is to generate the command signal basing on the current meas-ured in the electromagnet coil, so that the current should be main-tained on the preset level. Besides, the application configures and handles the digital analogue signals from the microcontroller (including the signals from the PWM signal generator, an A/C converter and the SPI interface supporting the communication with the SPI/CAN converter). To lend the controller a deterministic feature, the control algorithm is activated in the procedure of interruption from the timer. The time interval of this interruption is set to be 1 kHz. This value was selected basing on the trans-missibility characteristics of the power interface, obtained for the VI-MR, shown in Fig. 3. The gain Mg is derived from formula (1).