Tham khảo tài liệu 'contemporary robotics - challenges and solutions part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Adaptive Bio-inspired Control of Humanoid Robots - From Human Locomotion to an Artificial Biped Gait of High Performances 291 the compliance indicator K kz0 kre. During the SP and WAP the stiffness adjustment factor of leg impedance is kept invariable . ki ki const . During a WSP biped robot behaves as an inverted pendulum. A body mass displacement happens in this phase causing variation of the corresponding ground reaction forces at the foot sole. Consequently corresponding impedance adjustment factors ki i bl ị should be determined with respect to the contact force magnitudes Fl z as well as to their rates of changing Fl z . Algorithm uses force error eF Fz - F0z as well as rate of force error TV 7 0 e F Fl z Fl z as the indicators necessary for stiffness adjustment factor ki and damping adjustment factor bl modulation Fig. 5 . Depending on the signs less equal greater than zero of eF and eclF errors the proposed empirical algorithm calculates corresponding I II particular stiffness adjustment factors ki and ki . The valid value takes one that satisfies criterion given by the relation Ịíc 1 kj0 k kj0 see Fig. 5 . Identified stiffness adjustment min max factor ki takes a value within the range k e I k ki I . Damping ratio and stiffness factor are related each other according 19 . Changes of stiffness adjustment factor ki as one of leg impedance characteristics causes consequently changes of the damping ratio factor bl as presented in Fig. 5. When the amplitude of the ground reaction force Fl z in z-direction increases over its reference value Fz . eF Fl z F0 0 then the leg muscles should be relaxed. Accordingly stiffness of robot leg mechanism should be decreased proportionally and vice versa for eF F z F0z 0 . 292 CONTEMPORARY ROBOTICS - Challenges and Solutions Fig. 5. Flow-chart of the algorithm for determination of adaptive impedance parameters in a way that emulates natural leg impedance modulation with human beings Adaptive Bio-inspired Control of .
