Research On Dynamic Stiffness Identification And Control Of Flexible Joint With Adjustable Stiffness

The Flexible Joint with Adjustable Stiffness(FJAS) was introduced into thelegged robots, with which the joint stiffness could be adjusted in real-timeaccording to the different moving condition and terrain conditions, expect that FJAScan effectively reduce the contact force between the ground and the robot, as aresult, the FJAS can play a part in reducing energy loss and protecting the robotbody, besides that it can enhance the terrain adaptability. Some researchers havecarried out research in this field and designed several flexible joint models with theadjustable stiffness, but because of the lack of effective real-time dynamic stiffnessidentification method, which induces that the joint real stiffness was hard to got inreal-time, further which makes it hard to using the joint stiffness information as thefeedback to form a closed-loop control system, as a result limits the application ofFJAS to a large extent. Target at the problem, a deep study in the real-time dynamicstiffness identification of the FJAS was carried out firstly, on this basis, the study inthe stiffness and motion control of FJAS was carried out.Firstly, aiming at the nonlinear characteristics of joint torque in the FJAS, inthis chapter the Taylor expansion was introduced to substitute the nonlinear flexibletorque, then the Kalman filtering algorithm was used to identify the coefficients ofthe Taylor expansion, base of which the stiffness identification algorithm wasdeduced. Given the effect of the control parameters changing while the jointstiffness adjusting, parameters was decoupled at first, then the Taylor expansion wasexecuted, in this way the dynamic stiffness identification problem of FJAS wassolved. In addition, the joint moment of inertia and damping coefficients arerequired when the joint stiffness was identified, so identification of theseparameters was also studied.Secondly, aiming at the stiffness and motion control of the JVAS, on the basisof stiffness identification method, developed an effective closed-loop joint stiffnesscontrol method; on the basis of that the joint stiffness being controlled effectively,developed an effective closed-loop joint motion control method; combining thestiffness and motion control method of the JVAS, developed a stiffness and motionmixed control method.Finally, the simulation platform was established in accordance with the jointdynamic stiffness identification and control algorithm put forward in the frontchapters to verify the validity of these algorithms. Through analyzing on simulationdatas the parameters in the algorithms could be optimized, then the satisfying jointdynamic stiffness identification、joint stiffness and motion control system was achieved.