Research On Resolver Decoding Technology And Its Application In Servo Systems

In permanent magnet AC servo systems,the accuracy and speed of position detection will directly affect the overall system performance.Among many position detection methods,the resolver is widely used because of its high reliability,good anti-vibration performance,wide temperature range and strong anti-interference capability,especially in harsh environmental conditions such as high temperature,cold,dust,humidity and vibration.However,the output signal of the resolver is two-channel orthogonal analog modulated signals,which needs resolver-to-digital-converter(RDC)to obtain the rotor position information.Currently,specialized RDC chip is commonly used in applications,which has the advantages of simple use,high resolution,and strong reliability.However,the limited chip specifications,expensive prices and monopoly of foreign semiconductor companies limit the application of resolver in some applications with cost and size restrictions,as well as in the military industry.In this dissertation,the following research has been carried out with the aim of achieving the digital decoding of resolver in a localized scheme.Firstly,starting from the working principle of the resolver,the equivalent electrical model of the wire-wound sine and cosine resolver was established,and its mathematical expression was analyzed and derived.From the perspective of digital decoding,the demodulation method of the resolver output signal was studied,and the open-loop and closed-loop extraction methods of the rotor position information were analyzed and verified by simulation.The influence of non-ideal conditions such as amplitude imbalance and phase non-orthogonality on the closedloop angle solution was analyzed.Secondly,the design of resolver digital decoding control system was carried out.According to the application requirements of the project,a closed-loop angle observer was used as the position decoding algorithm.To address the problem of angle calculation delay caused by the demodulation filter in traditional digital decoding methods,the demodulation link was implemented inside the angle observer in the design of the control system to achieve delay-free angle decoding,which effectively improves the system bandwidth and decoding accuracy.Through the frequency domain analysis method and system simulation,the influence of several parameters on the performance of the system was studied.Finally,the software function of the resolver digital decoding control system was implemented in the GD32 microcontroller.Then,the hardware experiment platform of the resolver to digital converter module was designed and the decoding experiments were carried out.By connecting the motor with an encoder and the motor with a resolver coaxially,the position information output from the encoder as reference and the position information obtained from the resolver to digital converter module are sent to the upper computer for comparison and analysis under different working conditions such as stationary and rotating motors.The experimental data show that the digital decoding solution based on GD32 had a detection error of no more than 0.1° compared with the angle information obtained from encoder,and the decoding speed under the angle step is comparable to the performance parameters given in the datasheet of the special RDC chip.Finally,the designed resolver to digital converter module was used as the position feedback to build a vector control system of permanent magnet synchronous motor and conduct the related experiments.The experimental results show that the designed GD32-based resolver to digital decoding scheme can be applied to the vector control system,and the system has good speed response,control performance and certain anti-disturbance capability.