Hardware Design and Implementation of Optoelectronic Pod Control System Based on DSP

Zhigang Feng, Ming Jin
2017 International Journal of Hybrid Information Technology  
The optoelectronic pod always works in complicated environment, so it was impacted inevitably on various of elements such as Windage, Mechanical vibration, Load disturbance and so on. These random factors and nonlinear factors led to reduce the control precision, so much so that it can damage the hard-system of the optoelectronic pod. Traditional control system of optoelectronic pod always adopts PID control algorithm to eliminate errors between control target and actual feedback. However, the
more » ... back. However, the traditional PID can't track variational variables such in the complicated environment. It can led to lower the control precision and slow the speed of response. Self-adaption control system of optoelectronic pod adopts active disturbance rejection control (ADRC) technique which can track the mutational disturbance, estimates it and compensates it. In this paper, optoelectronic pod control system is designed and implemented by using TMS320F28335 to acquire the sensor signals, execute control algorithm, and drive the DC torque motor. The angular displacement sensors acquire the attitude angular displacement and the gyroscope acquires the attitude angular speed. The system can get attitude information of the optoelectronic pod with them. The motor diverters detect the driven current of motor to complete control feedback of DC torque motor. The EEPROM stores control parameters and sends relevant parameters according to DSP instructions. Experimental results indicate that DSP data processing unit can acquire the inner sensors data correctly in normal state, and perform control algorithms steadily in the disturbed environment. world advanced level (including America, Israel, Canada, French, Russia and etc...). They have developed many types of optoelectronic pods and largely equipped them for military. The new generation optoelectronic pods both adopt digital processing units and high integration density electronic chips to reduce bulk of pod. Control precision of optoelectronic pod has already reached 0.5urad. With these designs, the costing of optoelectronic pods had been largely decreased and application areas of pod have been enlarged. Lockheed Martin F-16 PANTERA pod is an advanced airborne electro-optoelectronic pod. PANTERA incorporates a high-resolution 3-5μm third generation forward-looking infra-red (FLIR), ahigh-resolution near-infra-red CCD daylight TV camera, an infra-red pointer, a dual-mode laser, and a laser spot tracker. With the development of aviation industry, the modern fighter aircraft has capability to cruise in the complex working conditions, so it brings a challenge for optoelectronic pod. The traditional control system of optoelectronic pod always adopts Proportional-integral-derivative (PID) control algorithm. PID control provides an efficient solution to control problems and make good performance in static precision [1] .System input is always step value (break value) and the output is slow variety, so it is impossible that slow variety can track break value. As differentiator of PID control is not realized in the physical layer, so PID control algorithm has to adopt approximate differential method. The method not only causes low accuracy but also impacted easily on noise. The integration element of PID control may lead to slowing system response and can't compensate the high frequency disturbance. The fuzzy controller has good robust and is effective for the nonlinear time-varying system. Based on Advanced Scale Factor and Smooth Handover, Fuzzy PID Composite controller (A-FPID) can achieve high performance in static precision and dynamic characteristic for stabilized platform [1]. However, Fuzzy PID control algorithm may produce a large overshoot in the implementation process. In the engineering, system engineers design the fuzzy rules based on their design experience, so the fuzzy rule leaks will appear inevitably in the extreme environment. Optoelectronic pods hang on the moving vehicle. The vibration of carrier and wind resistance result in the instability of optical sensors and jitter of obtained video [2, 3] .Specially, the vibration of carrier becomes unpredictable when the air force enter into low-level suddenly. To reduce the airborne vibration influence of optoelectronic pod on quality and stability, the irrotational displacement vibration isolation device was designed according to the parallelogram principle, vibration isolation theory and the analysis data of pod modal [4] . According to the need of reconnaissance mission, modern aircraft has to adopt low altitude fight, in this case, it generates severe vibration emerge inevitably. This vibration isolation device can't isolate completely vibrations, therefore, the disturbance compensation should be added to maintain dynamic stability of control system. In this paper, active disturbance rejection control (ADRC) application in the optoelectronic pod for disturbance rejection. Firstly, model of stabilized platform system is established, in which uncertain external load disturbance and unmodelled dynamics are regarded as one integrated disturbance. Then, using ESO to observe and compensate this integrated disturbance, and using the compensation loop of ADRC as the inner loop of traditional PID controller [5] . The Digital Signal Processor (DSP) operates efficiently ADRC algorithm. It can improve control performance and anti-disturbance ability for optoelectronic pod in the complex controlled environment. In this paper, the electric current loop is added to protect hard-system of airborne optoelectronic from locked-rotor current in the extreme environment. The paper is organized as follows. In the section 2, airborne electro-optoelectronic pod system model analysis is briefly summarized. The DC torque motor model is proposed to calculate its transfer function. According its orders, the extended state observer is built to estimate system disturbance. In the section 3, constructs system framework according to control requirement, and expounds module functions in detail. In the section 4, introduces the hard-system analyzes module circuits of system in detail. In the section 5, introduces DC torque motors in real time, then the detection signal feedback to DSP and achieves loop control with DC torque motors. Due to actuator, temperature protection was added to protect actuator from damaged by higher temperature. The AD7606BSZ analog-digital converter has 8 conversion channels with 16 bit in the chip, it can be selected two output modes (parallel bus, serial port). After AD7606BSZ converted 4 channels signals in sequence, DSP acquires digital data by ADC peripheral interrupt. Communication Interface Circuit Design Because of the SCI modules has difference between host computer serial ports in logic and voltage level [8] . The communication interface circuit realizes transformation between SCI module of DSP and host computer, and ensure that DSP can maintain communication steadily with host computer. The circuit was designed as figure 9, MAX3232 and MAX3488EESA were selected to achieve these requirements. The MAX3232 has 2 receivers and 2 drivers, and can run at data rates of 120kps while maintaining RS232 output levels. The schematic circuit was shown in figure 6-7, the chip charge pump requires a flying capacitor (C10, C11) and a reservoir capacitor (C12, C13) to generate the V+ and V-supplies.
doi:10.14257/ijhit.2017.10.8.03 fatcat:vaoa4d7ii5eyhezzwk3rkmb3me