This paper proposes a friction model for friction compensation of harmonic drive gearings. The model is composed of parallel viscoelasto-plastic elements and rate-dependent viscosity. Comparative experiments between the proposed model and the Generalized Maxwell slip (GMS) model have shown that the proposed model is advantageous especially in the region of presliding displacement. This paper also presents parameter identification method for the model.
At present, there are body-powered hooks and myoelectric prosthetic hands that trans-radial amputees can use for work. Though the body-powered hook has good workability in detailed works, the design of the hook spoils its appearance and the harness impairs the feelings of wearing. The myoelectric prosthetic hand has a natural appearance similar to the human hand and intuitive operability with a myoelectric control system. However, it is high cost and heavyweight. Because of these problems, many amputees use cosmetic prostheses especially in Japan. In this paper, we report a low-cost and lightweight electric prosthesis with three opposed fingers considering functionality and design. A simple mechanism to control fingers by a linear actuator contributes to satisfactory workability, lightweight, and low cost. A control system using an inexpensive distance sensor allows intuitive operability as the myoelectric sensor at low cost. A socket is easily removable so that users can wear properly as the situation demands. It has a sophisticated appearance as a tool and can be produced by a 3D printer. The total weight of the hand and socket is 300[g]. Evaluation tests utilizing Southampton Hand Assessment Procedure (SHAP) demonstrated that developed prosthesis was effective to operate light objects for daily use.
This paper introduces an implementation technique of sensor-less control on two joint robot manipulator. A great number of robots have been developed and most of them mount many kinds of sensors. However, use of the many sensors increase cost of robots and decrease reliance. Shimada et.al. have presented a unique sensorless control technique for electric motor driven mechanical systems. The feature of the technique is to mount mechanical springs on joints of robots. Furthermore, they have tried to extend the sensorless control technique to robots with revolutional joints. However, the performance of the presented observer was not enough to practical use. To fix the problem, we have tried to design time varying observer considering the time varying characteristics on the mounted mechanical springs. This paper introduces the simulation and experimental results of the presented control technique.
For the utilization of service robots, demonstrative experiments in real situations are necessary. Through the experiments, one can verify the effectiveness of research results and also can find new research issues. However, the legal systems and safety guidelines for the demonstrative experiments of the service robots are not established well. Hence, it is difficult to carry out the experiments effectively, which could degrade research progress for service robot utilization. Therefore, based on a case study in “Real World Robot Challenge”, which is a demonstrative experiment for autonomous mobile robots in outdoor public space, we proposed some basics of safety guidelines for the demonstrative experiments for mobile service robot in the paper. Specifically, the issues which must be considered in the public space demonstrative experiments and their explicit framework are clarified based on the international safety standards. In addition, we propose a risk assessment method and a risk management system of which the researchers are easy to use in the experiments, and by using these, some protective measures for the risks are developed which are feasible and suitable in the present situation. According to this, R and D activities in real situations will be promoted, which accelerate the utilization of service robots.
Compliant-parallel (C-P) mechanism is parallel mechanism that all joints are composed by deformable springs. In previous studies, since compliant mechanisms have a limited working area due to limitation in their structural deformation, the working area is limited in micrometer/millimeter-scale. From this background, the authors first improved a 1-DOF compliant joint to realize a wider range of working area by optimization of compliant structure, then developed a new 5-DOF parallel mechanism based on the new compliant joints. The new mechanism consists of a double DELTA mechanisms, connected on each end-effector by a newly developed 2-DOF rotational compliant joint. Because the proposed parallel structure conducts translational motions using only 1-DOF compliant joints, the mechanism achieves a wide range of translational working area. The prototype was developed to achieve assembly tasks for handling optical components such as lens and mirror. The evaluation tests reveal that the prototype has high precision within a wide range of working area. The proposed mechanism can be potentially applied to other applications, such as medical, semiconductor or space industries.