Seong-Sik Yoon

Safe Arm Design with MR - based Passive Compliant Joints and Visco - elastic Covering for Service Robot Applications

In this paper a safe arm with passive compliant joints and visco—elastic covering is designed for human-friendly service robots. The passive compliant joint (PCJ) is composed of a magnetorheological (MR) damper and a rotary spring. In addition to a spring component, a damper is introduced for damping effect and works as a rotary viscous damper by controlling the electric current according to the angular velocity of spring displacement. When a manipulator interacts with human or environment, the joints and cover passively operate and attenuate the applied collision force. The force attenuation property is verified through collision experiments showing that the proposed passive arm is safe in view of some evaluation measures.

Input preshaping control of the safe arm with MR-based passive compliant joints

In this paper, design and control of a safe arm with passive compliant joints (PCJ) are presented. A new manipulator with passive compliance property has been developed at KIST. Strategy for the joint control method is implemented. Because the PCJ is a flexible joint, unwanted vibration is occurred during the joint motion. To reduce this vibration, we use the input-preshaping method which is motivated by the input shaping technique (IST) based on impulse response. The control method for a time-varying system like the safe arm is described in detail. The result of simulations and experiments proves that a fast motion of the safe arm without residual vibration can be achieved.

Dynamic tactile restoration by time domain nonlinear filtering without forward modeling

When we use a tactile sensor, sensing mechanism and restoration of texture from electric sensing signals are important issues. The objectives of this research are to design a new texture sensing system and to develop a new signal processing algorithm which can restore various texture. The new texture sensing system is designed to get texture with high resolution and wide velocity range, which uses a PVDF sensor and has fixing components for several types of objects in precise condition. Next, a new signal processing algorithm is developed to restore texture. In the previous researches, forward model is needed and then it is inverted by using some regularized inversion formula in frequency domain, where there exist problems such as amplification of noise due to ill-posedness, modeling uncertainty due to orientation and position of PVDF films and silicon rubber, and difficulty to add nonlinear terms into model in frequency domain. While, in this paper, we model directly the relation containing transient-state from measured signals to texture by using model structure of multi-input multi-output nonlinear autoregressive moving average and a time domain least squares estimation. The direct modeling can be done by the use of F/T sensor which is not used in the previous researches. Finally the several texture is experimentally reconstructed from sensing signals using the developed signal processing algorithm.