In this paper, we focus on the maximization of the jump height of a serial link robot. The jump height maximization problem is formulated as a nonlinear programming problem, where torque patterns to drive joints in the robot are decision variables and the objective function is an inexplicit function whose value is obtained as an output of a jump simulator. As a previous reasearch, an approximate solution method using a genetic algorithm was proposed for the jump height maximization problem. In the research, some interesting joint drive torque patterns were found by the method, but it costed much time to obtain a drive torque pattern. In order to improve the accuracy of the obtained solution and shorten the computational time, in this paper, we propose a new solution method based on particle swarm optimization (PSO) .
Metal spinning is a plastic forming process that forms a metal sheet by forcing the metal onto a rotating mandrel using a roller tool. A novel metal spinning machine was designed in which the roller is directly driven by linear motors. We aim to form non-axisymmetric products by controlling the pushing force of the roller so that the roller can quickly track the changing radius of the mandrel. Our experimental results show that the linear motors substantially improve response of the force control and non-axisymmetric products can be rapidly formed. Open-loop force control without a force sensor was also studied. It exhibited a comparable performance to closed-loop control with regard to the forming time.
The final goal of this research is to clarify and obtain the fundamental control strategy of human's pinching movements by using a redundant musculo-skeletal dual finger model. First, a mathematical model of a 3 D.O.F. musclo-skeletal dual finger in which each finger is actuated by six nonlinear redundant muscles is formulated. Next, the kinematics and dynamics considering geometrical constraints for the finger-object system are described, and a sensory-motor coordinated feedback control law is designed to realize stable pinching simultaneously with posture and position regulation. Then, some numerical simulations are performed and the results suggest that the co-contraction of the digitorum muscles makes it possible to realize human-like pinching movements. Also the convergence of the closed-loop dynamics is proved by using a concept of “Stability theory on a manifold.”
To design a tactile sensor that can measure direction and distribution of force, common strategy is to add a mechanical tab on top of four sensing elements. The tab translates force direction information to the sum and difference of the elements' output. However, quantitative criteria for the evaluation of the sensor has not been proposed. In this paper, we propose to use singular value decomposition (SVD) to measure S/N ratio and gain at the same time. We also applied the proposed criteria to optimally design the reflector pattern of the optical type tactile sensor.
This paper describes self-reconfigurable robot CHOBIE that adaptively construct a mechanical structure. CHOBIE modules have slide motion mechanisms and transform the structure by synchronous movements. First of all, mechanical features of the robots are described. Second, as an effective control method for the synchronous robotic system, a new scheme “temporary leader” is introduced. Some experimental results show the validity of the scheme. Third, scalability of the system is discussed. In particular, we focus on problems of synchronous of the modules and amount of data processing in the system composed of large number of modules.
This paper describes development of a micro-scissors type haptic device with operational feeling of cutting soft tissue. Micro-scissors are a type of surgical instrument, which is frequently used in brain surgery under a microscope. The goal of this research is to realize a brain surgery simulator with a micro-scissors type haptic device. In order to feed back small and accurate force with high response, two DC motors are used as actuators, and two crank-lever mechanisms are applied as decelerators to reduce backlash and slipping, and H-slit force sensors with high strain sensitivity are implemented. In an experiment for performance evaluation of the device, the device is controlled to present computed force through sensor feedback, using the sensor compensation based on calibration, which is unique to the micro-scissors type haptic device with a blade spring. Results of the evaluation experiment are presented to prove that the device is able to convey the feel of cutting.
In this paper, we propose a novel tactile sensor in which array of rigid elements is inserted to measure tangential force in addition to perpendicular force. The sensor structure is based on a tactile sensor using pressure sensitive rubber covered with elastic body and single-sided electrode sheet, which was developed in our previous study, in order to derive distribution of pressure magnitude. The principle is described, and two dimensional finite element analysis is carried out. Numerical results show that the perpendicular force and the tangential force can be derived simultaneously with the proposed sensor, and the effect of dimensions of the rigid element is discussed by both mechanical prediction and numerial results. A 3 × 3 unit-cell tactile sensor with pressure sensitive rubber and electrode sheet is prototyped, and experiments are undertaken using 6-axis force sensor as a reference. Experimental results having characteristics in dependence on tangential force and perpendicular force are compared with analytical results. The contributions of rigid element to sensor output is observed experimentally in agreement with simulations, and sensor properties are described.
This paper presents a development of multi-fingered hand, which is modularized and can be attached to life-size humanoid robots. The developed hand has four fingers with 17 joints, which consist of 13 active joints and 4 linked joints. A miniaturized 6-axes force sensor is newly developed and is mounted on each fingertip for improving the manipulability. A main node controller with I/O, motor drivers, and amplifiers for 6-axes force sensors are also newly developed. These components are equipped in the hand for modularization. The developed hand is designed so as to realize about 8 [N] forces on the pad point of stretched finger, supposing transmission efficiency of drive system is 55%. In this paper, the mechanisms and specifications of hand module, electrical system, and fundamental experimental results are also introduced.
We propose a method of approximating a continuous curve by Active Cord Mechanism. In this method we only use deformation parameters of a curve such as curvature and torsion, and do not use coordinates of a curve, so the proposed method does not include solution of nonlinear equations and the calculation cost is less than former methods. We also discuss the convergence of approximating error in this method and show the error is inversely proportional to square of the number of links in planar case. The proposed method is simple and easy to apply, so it is useful for control of multi-joint robots, particularly for control of snake-like robots. We have implemented the proposed method on real snake-like robots and shown the merit of the proposed method by experiments. This result shows the proposed method is effective for study of snake-like robots.