tailieunhanh - Industrial Robotics Theory Modelling and Control Part 16

Tham khảo tài liệu 'industrial robotics theory modelling and control part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Friction compensation in hybrid force velocity control for contour tracking tasks 891 a b Figure 13. Tangential velocity signals with no friction compensation and with SFC and AFC for the disk in the A position. a implicit control b explicit control. The mean value of the normal force and tangent velocity RMS error for the different experiments is then reported in Table 1. From the results presented it can be deduced that a friction compensation strategy is indeed necessary especially for the explicit control law. This is motivated by the fact that the inner joint position control loops in the implicit control law are somehow able to cope with the friction effects. However it has to be noted again that the implicit control law requires a greater tuning effort than the explicit one although from another point of view it has the advantage that it can be applied to a pre-existing motion control architecture . The Adaptive Friction Compensation strategy provides definitely the best results for the explicit control scheme both in terms of normal force and tangential velocity while for the implicit control law the performance obtained by the Adaptive Friction Compensation scheme and by the Static Friction Compensation scheme are similar. In any case the great advantage for the AFC of being a model-free scheme . no preliminary experiment is required to derive a friction model and robustness to variation of the friction parameters is assured makes it more appealing to be applied in a practical context. It is worth stressing that the AFC strategy is effective in reducing the normal force and tangential velocity errors especially when the joint velocity sign changes. This fact can be evaluated by considering the resulting two joint velocities that would be necessary in order to achieve the required tangential velocity of 10 mm s for disk A . They are reported in Figure 14 compare with Figures 12 and 13 for example at time t s when the velocity of the first joint .