Abstract: The investigated autonomous control system for a squeeze mode magnetorheological (MR) vibration isolator is based on an ultra-low power microcontroller MSP430F5529. The design structure of the control system and the dedicated real-time system are briefly presented and the laboratory testing data are summarised.42501
Key words: MR Vibration Isolator, Control System, Controller
1. INTRODUCTION
The last decade has witnessed a major interest in squezee-mode MR vibration isoslators (VI-MRs) (Farjoud et al., 2011; Kim et al., 2008; Zhang et al., 2011). The majority of previous research has been focused mainly on theoretical studies, e.g. Jolly and Carlson (1996) and Stanway et al. (2000). It is worthwhile men-tioning that certain solutions for these type of VI-MRs have been patented (Kim, 2012; Sapiński, 2013).
The investigated autonomous control system (ACS) is de-signed to be used for control of a prototype squeeze-mode MR vibration isolator (VI-MR). The VI-MR is intended for use as an actuating element in a semi-active engine automotive mount system designed to reduce the engine’s vibrations due to fluctuat-ing inertia forces (caused by unbalanced element of the crank system), to fluctuations of the drive torque transmitted from the engine onto the drive system components and to the action of some random forces (Kamiński and Pokorski, 1983; Snamina and Sapiński, 2014).
The ACS is based on an ultra low power microcontroller MSP430F5529 (MSP430) (Texas Instruments INC, 2013). Prior to the fabrication of ACS, testing was done on a previously devel-oped power driver dedicated for VI-MR and based on an integrat-ed interface VNH2SP30-E (Rosół and Sapiński, 2014).
The ACS requires a dedicated real-time clock system, to ena-ble the measurement of process variables and to develop the control method with the predetermined sampling period (Philip and Laplante). The quaranteed constatnt sampling period enables the usie of the theory of discrete control systems in developing control algorithms for VI-MR. Besides such approach allows to employ model-based design method in simulation, testing and implementation of regulators on the target hardware platform.
Measurement data from the ACS are monitored and pro-cessed using a serial bus Controller Area Network (CAN) (Bosch GmBH, 1991). This bus was selected as it is intended for use in control of the VI-MR to be installed in the engine mount in the
vehicle where CAN acts as the primary data transmission inter-face.
The engineered ACS was tested in the laboratory conditions in two configurations: the open loop and in the feedback loop (with a PID controller) systems. Testing was done under the loading applied through the electromagnet coil whose resistance and induction were similar to the parameters of the control coil in the VI-MR.
2. DESIGN STRUCTURE
The block diagram of the ACS, shown in Fig. 1, comprises the following units: the MSP430 block with analogue and digital signal outputs, the measurement block, the CAN interface, the power-supply and the USB interface.
The key compnent of the ACS is the MSP430 supporting the measurement and control application. The MSP430 features high program memory and data memory capacity, numerous integrated peripherals (USB, SPI, 12C, UART, an A/D converter,
a multiply unit) and the supply voltages can be generated via
an USB port. The major technical parameters of the MSP430
are summarised in Tab. 1.
The MSP430, the measurement block and the CAN bus block are supplied with voltages +5 V and +3/3 V from the power supply block. The ACS may be supplied via a micro-USB port (+5 V) or from a power supply unit delivering the voltage in the range (+3.3, +12) V.