Design, Modeling and Control of Bionic Knee in Artificial Leg

The biped robot with heterogeneous legs (BRHL) greatly facilitates the development of intelligent lower-limb prosthesis (ILLP). In the BRHL, the remaining leg of the amputee is simulated by an artificial leg, which provides the bionic leg with the precise gait following trajectory. Therefore, the artificial leg must closely mimic the features of the human leg. After analyzing the motion mechanism of the human knee, this paper designs a four-link bionic knee in light of the coexistence of rolling and sliding between the femur, the meniscus and the tibia. Drawing on the driving mechanism of leg muscles, two pneumatic artificial muscles (PAMs) were adopted to serve as the extensor and flexor muscles on the thigh. The two PAMs move in opposite direction, driving the knee motions in the artificial leg. To overcome the complexity of traditional PAM modelling methods, the author set up a PAM feature test platform to disclose the features of the PAMs, and built static and dynamic nonlinear mathematical models of the PAMs based on the test data. Next, a proportional-integral-derivative (PID) closed loop controller and sliding mode controller was designed for the bionic knee, referring to the kinetics equation of the knee. Through experimental simulation, it is confirmed that the proposed controller can accurately control the position of the four-link bionic knee, and that the designed bionic knee and PAM driving mode are both correct

A Fractional Order Proportional-Integral-Derivative Controller for Series Continuous Stirred Tank Reactor System

For series continuous stirred tank reactor system (CSTR), it is a complex problem to finetune the fractional order proportional-integral-derivative controller (FOPID). To solve the problem, this paper presents a parameter tuning method based on intelligent optimization genetic algorithm (GA) and integral time absolute error (ITAE). Firstly, the series CSTR system was mathematically modelled by vectorized modules, and an FOPID control system was established. Meanwhile, the intelligent optimization GA was introduced under the ITAE rule, and the empirical PID control parameters were taken as the initial values for iteration, aiming to enhance the effect of the search for optimal solution. To verify its superiority, the FOPID controller optimized by GA was compared with intelligent optimization GA and empirical PID controller through simulation. The results show that the optimized FOPID system achieved much better control effect and stronger anti-interference performance than the contrastive methods