Comparative analysis of speed decoding algorithms for rotary incremental encoders

Motion control process in modern automation technology and industry requires highly accurate speed information with high bandwidth. Incremental encoders are widely used as rotary feedback position and speed sensors which convert the motor position and speed information into coded electrical pulses. An accurate speed decoding system is therefore needed to extract necessary position and speed information from encoder output, which is further required by the motion control process. The level of accuracy and bandwidth highly depend on resolution of encoder being used as well as data processing technique. In this thesis, different incremental encoders and state-of-the-art speed decoding algorithms are discussed. These algorithms are implemented in Matlab Simulink and a comparative analysis is done based on accuracy, rapid response and wide speed range application. Further, the best choice is made based on this comparison and corresponding speed decoding algorithm is implemented in Xilinx FPGA. Analytical simulation results are presented in this thesis

FPGA-Based Velocity Estimation for Control of Robots with Low-Resolution Encoders

Robot control algorithms often rely on measurements of robot joint velocities, which can be estimated by measuring the time between encoder edges. When encoder edges occur infrequently, such as at low velocities and/or with low resolution encoders, this measurement delay may affect the stability of closed-loop control. This is evident in both the joint position control and Cartesian impedance control of the da Vinci Research Kit (dVRK), which contains several low-resolution encoders. We present a hardware-based method that gives more frequent velocity updates and is not affected by common encoder imperfections such as non-uniform duty cycles and quadrature phase error. The proposed method measures the time between consecutive edges of the same type but, unlike prior methods, is implemented for the rising and falling edges of both channels. Additionally, it estimates acceleration to enable software compensation of the measurement delay. The method is shown to improve Cartesian impedance control of the dVRK

Design of Real-Time Hardware-in-the-Loop TV Guidance System Simulation Platform

This paper presents a novel design of a real-time hardware-in-the-loop (HIL) missile TV guidance system simulation platform, which consists of a development computer, a target computer, a turntable, a control cabin, and a joystick. The guidance system simulation model is created on the development computer by Simulink® and then downloaded to the target computer. Afterwards, Simulink Real-Time™ runs the model in real-time. Meanwhile, the target computer uploads the real-time simulation data back to the development computer. The hardware in the simulation loop is TV camera, encoders, control cabin, servomotors, and target simulator. In terms of hardware and software, the system has been simplified compared with the existing works. The volume of the turntable integrating the target simulator and the seeker simulator is about 0.036 cubic meters compared to the original 8 cubic meters, so it has a compact structure. The platform can perform the closed-loop control, so the simulation has high precision. Taking the TV guidance simulation as an example, in the case of target maneuvering, the final miss distance of the TV guidance missile is 0.11812 m, while the miss distance of the original system is 13 m. The trajectories obtained from the HIL and mathematical simulations substantially coincide. So the simulation results show that the proposed HIL simulation platform is effective