| The satellite scanning drive control system is an important part of the whole satellite system,which is directly related to the completion of the whole satellite system task.With the development of applications in the fields of national economy and military,the load of spacecraft represented by microwave load has higher requirements for the weight,pointing accuracy and speed stability of scanning drive mechanism on satellite.The traditional scanning driving mechanism is driven by electromagnetic motor which has a lot of problems,such as large volume and heavy weight.It also has long electromagnetic response time when it is cut off,and it can not meet the requirements of fast start-up,fast stop,and fast arrive stable operation.Besides,gear and other transmission devices are needed in the traditional scanning drive mechanism.However,gear transmission will bring about some problems such as gear clearance,return error and jitter,which will affect the movement performance of scanning mechanism,and can not meet the needs of the new generation of high load scanning drive mechanism in precision.Since the ultrasonic motor has the characteristics of direct drive and self-lock,it can work without the deceleration,transmission and self locking device,which greatly simplifies the design of scanning drive mechanism,and makes the whole mechanism more compact and lighter in weight.At the same time,the ultrasonic motor has the characteristics of low rotation speed,high position resolution,and no electromagnetic interference,which makes the ultrasonic motor an ideal driver for a lightweight,low-speed,high-precision scanning drive mechanism.Therefore,based on the investigation of the driving modes of the scanning drive mechanism at home and abroad,aiming at the demand of microwave load scanning drive technology,this paper proposes a kind of light-weight,high-precision,and high-speed stability scanning drive mechanism which is driven by ultrasonic motor.In this thesis,a lightweight spatial scanning drive mechanism based on TRUM-60 USM has been designed,the weight is just 2.35 kg,which is reduced up to 15%compared to the traditional stepper motor plus harmonic reducer drive scheme.According to the overall structure scheme of scanning mechanism driven by ultrasonic motor,selecting suitable main components such as drive motor,closed-loop control and angle measuring unit;using the sleeve connection method to ensure the coaxiality between the axis of the motor and the spindle through proper fitting of the sleeve,and it can ensure that the motor has a certain degree of freedom in the axial direction;choosing the bearing,shafting and other parts reasonably.The scanning mechanism makes the structure of the whole mechanism compact and small,and eventually achieves lightweight,fast response design requirements.In order to study the motion control of scanning drive mechanism driven by ultrasonic motor,test its pointing accuracy and speed stability,and cooperate with21-bits absolute photoelectric encoder as position feedback sensor,the whole precision drive control system was constructed.Then the detailed design was carried out from hardware and software.The ultrasonic motor drive control circuit was designed with PSoC 5LP as the main controller,and its constituent modules: signal generating circuit,push-pull transformer circuit which consists of push-pull power amplifier circuit and step-up transformer,inductance matching circuit and feedback module were also respectively designed.This method greatly reduced the size of the drive controller and had important implications for the lightweight implementation of the entire scanning drive system.With the new control scheme of two-stage control,an independent hierarchical control of the amplitude and phase of the ultrasonic motor control signal was achieved,the control scheme and the debugging process were simplified,and the system performance was improved.In the software design part,the overall flow of the system was introduced.The PSoC Creator integrated development environment was used to initialize each module,and control the start,stop,forward and reverse motion of USM.The PC as the upper computer implemented the serial communication of the upper and lower computer,and the photoelectric encoder data transceiver function.Improving the steady-state pointing accuracy and speed stability is a problem that the entire scanning drive control system must focus on.To solve this problem,this paper compared and tested the control strategies of USM.A multi-functional upper computer operation interface — VC# was designed to realize the function of synchronously displaying and saving the movement position and rotation value of the scan drive mechanism.After analyzed and compared the commonly used methods such as fixedgain PID control algorithm,fuzzy control algorithm,neural network PID control algorithm and etc,according to the nonlinear and time-varying characteristics of ultrasonic motor in the control process,a variable structure incremental PID control algorithm based on expert rules was proposed,which overcame the problem about parameters and structure modification.Finally,the experiments of direction control and speed stability control of the scanning drive mechanism were performed.The experimental results show that when the scanning drive mechanism is pointing at 20°,the steady-state pointing accuracy is better than 2 ",and the speed stability of the scanning drive mechanism is better than ±1% at 3.3rpm,which meet the requirement for high precision and high stability control of the scanning drive system mechanism. |
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