Study On The Current Controller Based On FPGA For A3-DOF Permanent Magnet Spherical Motor

The 3-DOF permanent magnet(PM)spherical motor is widely applied because of its advantages of three-dimensional characteristics,high mechanical integration,small volume,high accuracy and energy saving.However,The complex motion control of PM spherical motor.There are many problems,such as the number of stator coils,the closed loop current control,and the difficulty of parallel control of each coil.Firstly,in this paper,it introduces its basic structure of the 3-DOF PM spherical motor.Its unique operating principle is also explained.Then the torque modeling of permanent magnet spherical motor is established in this paper.Then,the paper analyzes the influence of the structural parameters of the coil of the spherical motor on the torque,and puts forward the control method of controlling the coil current to control the motor operation,and establishes the armature current control model.The armature current control model highlights the requirement of parallel closed loop control for multiple stator currents at the same time.The proposed model of the armature current control provides a theoretical reference for the control system.Secondly the current control commonly used algorithm analysis,to determine the coil current is controlled by PI,by controlling the PWM waveform duty ratio control bridge drive circuit to achieve the precise closed-loop control coil current,and the use of MATLAB current on single coil control scheme in the following experiments,confirmed the effectiveness of the proposed scheme.In this paper,the spherical motor model consists of 12 sets of parallel control stator coils.The coil current control scheme is parallel connected,and the M function is used to calculate and distribute the current of each coil during the movement of spherical motor.Finally,the MATLAB is applied to simulate the parallel control of the coil under different operation modes of the spherical motor,and further verify the effectiveness of the multi coil parallel PI current control scheme.Finally,according to the multi coil parallel PI current control scheme and the advantages of FPGA parallel control,the design scheme of the core processor based on FPGA for the current control system is worked out.Based on the idea of hardware and software co design,the design of several main functional modules,such as PI regulator,filter,PWM modulation and switching,is completed by digital hardware,and the current controller design and debugging test of spherical motor are completed.The tests of the control system have been completed to verify that the current controller of the spherical motor meets the requirements for close-loop and accurate control of multiple coils.