Due to the limited control bandwidth of pneumatic artificial muscles, joint stiffness characteristics and their effects on safety and performance of human-friendly robots should be considered in the frequency domain. This paper introduces the concept of effective dynamic stiffness and validates its model with the Stanford Safety Robot. Experimental results show that the dynamic stiffness demons...

Cancer is now a global concern, and control of the function of cancer cells is recognized as an important challenge. Although many aggressive chemical and radiation methods are in practice to eliminate cancer cells, most imply severe adverse toxic effects on patients. Taking advantage of natural physical differences between cancer and normal cells might benefit the patient with more specific cy...

This paper proposes a new impedance control algorithm based on a variable stiffness-matrix, for parallel-link manipulators without the measurement of the tip position. It assumes that only the link lengths and velocities as well as the contact force at the tip are measured, and that the motion range is small around an operating point so that the nonlinear dynamics can be linearized. One of the ...

Cancer is now a global concern, and control of the function of cancer cells is recognized as an important challenge. Although many aggressive chemical and radiation methods are in practice to eliminate cancer cells, most imply severe adverse toxic effects on patients. Taking advantage of natural physical differences between cancer and normal cells might benefit the patient with more specific cy...

We consider the use of linear parameter-varying methods for the control of stiffness hysteresis in vibration isolation systems. We assume that the hysteresis model is known, and we describe it using a stiffness parameter that takes values in a compact convex set. The proposed parameter-dependent controller is continuously scheduled based on real-time measurements or estimates of the stiffness, ...

This paper addresses the problem of accuracy and coupled stability of stiffnesscontrolled series elastic actuators, where the motor is modeled as a non-backdrivable velocity source, and the desired value of virtual stiffness is above the physical stiffness of the compliant element. We first demonstrate that, within the mentioned conditions, no linear outer-loop force control action can be appli...

The force regulation and inevitable positional inaccuracy of traditional control system can be compensated by the compliance/stiffness mechanism. The compliance/stiffness of a robotic mechanism is usually modeled by a 6 by 6 symmetric positive definite matrix at an equilibrium point using screw theory. When an external wrench is exerted on the mechanism and the mechanism moves away from its equ...

This paper focuses on the performance evaluation of the parallel manipulators for milling of composite materials. For this application the most significant performance measurements, which denote the ability of the manipulator for the machining are defined. In this case, optimal synthesis task is solved as a multicriterion optimization problem with respect to the geometric, kinematic, kinetostat...

This paper explores a passive control strategy with variable stiffness actuation for swing movements. We consider brachiation as an example of a highly dynamic task which requires exploitation of gravity in an efficient manner for successful task execution. First, we present our passive control strategy considering a pendulum with variable stiffness actuation. Then, we formulate the problem bas...

Recent research in robotics focuses the attention on the control of compliant actuators to improve safety and to make the interaction with humans more natural. Lightweight construction, real elasticity directly integrated into the joint and control of joint compliance seem to play the most important role for improving safety in human-machine interaction. Humans are intrinsically elastic and the...