“The three-degree-of-freedom aircraft flight attitude simulation test bench is a comprehensive test equipment integrating mechanical technology, control technology, sensor detection technology and computer technology. As a space motion mechanism, it is the key equipment for the dynamic performance test of the aircraft. It is mainly used to simulate the motion attitude of the aircraft, providing a simulation environment that is very close to the actual situation for the aircraft. Performance inspection has high application value in national defense and civilian use.
The three-degree-of-freedom aircraft flight attitude simulation test bench is a comprehensive test equipment integrating mechanical technology, control technology, sensor detection technology and computer technology. As a space motion mechanism, it is the key equipment for the dynamic performance test of the aircraft. It is mainly used to simulate the motion attitude of the aircraft, providing a simulation environment that is very close to the actual situation for the aircraft. Performance inspection has high application value in national defense and civilian use.
Based on the MSP430 control core, this paper designs a three-degree-of-freedom simulation test bench, and completes the given task requirements.
1. The overall plan of the system
The system is mainly composed of MSP430 control core, power management module, motor control module and wireless communication module. Its structural block diagram is shown in Figure 1.
The real-time position of the turntable is fed back to the microprocessor by the rotary encoder for processing. The stepper motor uses PID algorithm for regulation, while the DC brushless motor uses fuzzy control algorithm. In the software design, the feedback information of the encoder is collected in real time to realize the closed-loop control of the whole system.
2. System hardware design
The hardware of the system mainly includes: main control circuit, power management circuit, motor driver and wireless communication circuit. The system structure is shown in Figure 2.
2.1 MSP430 main control circuit
The core control of the system adopts TI’s MSP430 series microcontroller MSP430F149, which is mainly characterized by a high degree of functional integration, easy expansion, internal integrated watchdog timer, and 16-bit timers TImer_A and TImer_B with their own capture/compare registers to support PWM It has the characteristics of output function and ultra-low power consumption. It integrates 60 KB FLASH memory and 2 KB RAM on-chip and provides 256 B information FLASH at the same time, 64-pin square flat package. The microcontroller can also be serially programmed in-circuit without the need for an external programming voltage. The specific distribution of the system I/O ports is as follows: P1 port is used to receive the feedback signal of the rotary encoder; P2 port is the interrupt port; P4 is used to drive the PWM signal output of the DC brushless motor; P5 port is used to drive the stepper motor. Wave signal output; P6 is used for the control signal output of the motor driver.
2.2 Power Management Circuit
The whole system includes 3.3 V, 5 V, 12 V, 24 V four voltage environments. Among them, 3.3 V supplies power to the microcontroller system, 5 V supplies power to the rotary encoder, 12 V is directly drawn from the AC/DC transformer to supply power to the drive circuit, and 24 V is directly drawn from the AC/DC transformer to supply power to the motor. 5 V is obtained from 12 V through the HDW20-12S05 power module, as shown in Figure 3. 3. 3 V is obtained by 5 V through AMS1117 chip, and the circuit is shown in Figure 4.
2.3 Motor driver
The stepper motor driver adopts 2605AD driver. 2605AD is an equal-angle constant force-distance subdivision driver, the driving voltage is DC 24-60 V, the adaptation current is below 5.0 A, and the outer diameter is 57-86 mm. Various types of two-phase hybrid stepping motor. The driver adopts a circuit similar to the servo control principle, which can make the motor run smoothly at low speed, with almost no vibration and noise. The motor has a large torque at high speed, and the positioning accuracy can reach up to 25,600 steps/rev.
The brushless DC motor adopts a control driver, which is a closed-loop speed controller, adopts IGBT and MOS power device, and uses the Hall signal of the brushless DC motor to perform closed-loop speed control after frequency multiplication. There is no PID speed regulator in the control link. The system control is stable and reliable, especially at low speed, it can always reach the maximum torque, and the speed control range is 150r/s ~ rated speed.
2.4 Wireless Communication Circuit
Through the RS 232 level conversion chip in the serial port drive circuit, the communication between the single-chip microcomputer and the PC can be realized, and the channel of man-machine dialogue activity can be established. The SRWF-1 wireless communication module produced by Sangrui has stable performance, small size and easy installation. Using the MAX3232 chip, it can complete the conversion between TTL level and RS 232 level, and realize serial communication between the communication module and the PC. Its circuit schematic diagram is shown in Figure 5.
3. Control strategy
3.1 Stepper Motor Control Strategy
Conventional PID controller has the characteristics of simple algorithm, good stability, high reliability, easy value design and wide adaptability. It is the most widely used type of basic controller in process control. However, when the process starts, ends or greatly increases or decreases the setting, the system output will have a large deviation in a short period of time, which will cause the integral accumulation of the PID operation, causing the control amount to exceed the limit corresponding to the maximum allowable operating range of the actuator. The control quantity will cause a large overshoot of the system, and even cause a large oscillation of the system, which is absolutely not allowed in production. In the integral separation control room, when the deviation between the controlled variable and the set value is large, the integral action is cancelled; when the controlled variable is close to the given value, the integral control is introduced to eliminate the static error and improve the control accuracy. According to the actual situation of the three-degree-of-freedom turntable, the algorithm is improved on the basis of the integral separation PID control algorithm, combined with the incremental PID control algorithm to control the motor, and the experiment has obtained a good control effect.
3.2 BLDC Motor Control Strategy
The principle of the fuzzy PID controller is to input the deviation e and the deviation change rate ec of the input PID regulator into the fuzzy controller at the same time. The F controller in the figure is actually composed of three sub-fuzzy controllers, which adjust the three parameters respectively, and then input the obtained corrections to the PID adjustment after fuzzy, approximate reasoning and clarity respectively. In the controller, the three coefficients are corrected online in real time, so that the controlled object has good dynamic and static performance.
In this paper, the MSP430F149 single-chip microcomputer is used as the main control chip, the stepping motor and the DC brushless motor are used as the driving components, and a three-degree-of-freedom turntable with relatively high precision is produced through software programming. After the rotation control of the turntable, it is proved that the turntable can rotate smoothly and accurately according to any given position information, with good dynamic performance, strong system stability and anti-interference ability.
The three-degree-of-freedom turntable not only has high application value in the fields of national defense and military such as aviation, aerospace and navigation, but also has a very broad application prospect in the civilian field, but it still has a long way to achieve the high precision and high intelligence required by people. The road to go requires unremitting exploration and research.