In this paper, we propose a method of action based perception categorization for a legged robot to move to any destination in the environment. Once the robot acquires the relationship between actions and the changes of the view, it can generate the motion with respect to the observed scene. By utilizing this relationship, it reaches the desired position by feeding back the difference between the goal view and the current one. We call a group of motions based on the relationship a motion repertory. The motion repertory consists of sets of data of robot motion, which are compressed by the wavelet transform, and motion pattern of visual features. The validity of the method is shown by a preliminary experiment.
This paper discusses a sufficient condition for manipulation of Envelope Family, where multiple contacts are allowed between chains and object (or environment) . All chains are assigned by either position controlled chain (P-chain) or torque controlled chain (T-chain) . While the object motion under multiple contacts can not be uniquely specified by T-chains only, we show a sufficient condition ensuring that a given set of torque commands for T-chains always move the object toward the goal along the surface of P-chain (or a fixed environment) . Experiments as well as simulations are also shown to verify the basic idea.
This paper analyzes the indeterminate grasp force in power grasps or enveloping grasps and shows that its region is a bounded hyper-polyhedron. In power grasps a hand grasps an object at multiple points on the surface of the hand. If the hand and the object are modeled as rigid bodies, then it is known that the grasp force is in general not determined uniquely even if joint torques are given. We have already shown that the sliding directions of the contact points are restricted in power grasps to be consistent with rigid body motion. Static friction force acts only in the opposite direction of sliding. This characteristic of friction leads to our previous conclusion that the grasp force is also restricted. This paper shows that the region of the indeterminate grasp force is a bounded hyper-polyhedron that is not necessarily convex. The force that requires maximum friction exists at the vertices of the polyhedron. We present a simple algorithm for computing the vertices of the hyper-polyhedron. It can efficiently compute the coefficient of friction sufficient to maintain static equilibrium given an external disturbance and joint torques taking the indeterminacy of the grasp force into account.
This paper proposes a cylindrical tactile sensor that can simultaneously detect the contact angle, the contact position and the magnitude of the contact force for robot hands. This sensor consists of an inner frame with light sources and an outer shell suspended by two elastic rings. Since a two-dimensional position sensitive detector (PSD) is installed at the same section of the elastic ring, the output of the PSD directly corresponds to the displacement of the elastic ring. It was confirmed experimentally that the measurements concerning the contact angle, the contact position, and the magnitude of the contact force could be carried out with good accuracy by means of simple expressions. Consequently, this cylindrical tactile sensor is considered to be effective as the tactile sensor for robot hands.
A cooperative control method for multiple robots of single object transportation is proposed, which is applicable to unknown environment. In this method, all robots are controlled by the same algorithm, and they can have different objective tasks simultaneously. A task is expressed as the desired position of the object and the associated weight matrix, and each robot can set its own desired position and weight matrix independently of the other robots' tasks. By the proposed method, the robots can cooperatively transport the object to the composite desired position which is the weighted mid point of the desired positions set by all robots, without communicating their tasks with one another. The forces between the robots and the object are controlled as equally as possible during transportation. Furthermore, the internal forces can be suppressed only if some robots in danger of applying large forces broadcast on/off signal to the other robots. Accordingly, this method requires little amount of real-time communication among the robots and does not depend on the number of robots. Owing to these features, the method can deal with the situation where one robot has “path tracking task” and another robot which detects an obstacle has “obstacle avoidance task”; that allows cooperative object transportation with obstacle avoidance in unknown environment. The effectiveness and usefulness of the method are ascertained by computer simulation and experiment.
Dynamical interferences have been thought that they should be erased to improve control accuracy. However it may be possible to improve performances of total motion using the interferences. In this paper, we propose a method to acquire a kind of machine intelligence to utilize dynamically interfered motion. The machine intelligence is defined here as an ability that the machine can find by itself a way to use dynamical interferences and nonlinear friction to obtain a desired motion. We propose a strategy how a machine uses effects of the dynamical interferences, and how it acquires the way to achieve an objective motion. In this paper, the desired motion is traveling of a 1-link mobile manipulator by using interfering motion of the mounted link, which does not possess driving motors nor brakes. The proposed method is composed of functions to give the machine sample motions using Fourier cries and to improve the Fourier coefficients by evaluating the motion results based on a function used in Genetic Algorithm as a fitness function. Further, an ability to avoid collisions between mounted manipulator and floor is added to the traveling ability to confirm that the proposed method could be adapted to plural objectives. We confirmed by simulations and real experiments that the mobile manipulator could find effective motion that makes it travel forward without colliding against the floor.
The residual vibration reduction control method for the point-to point control of a two-link flexible robot arm by use of the optimal trajectory planning based on the genetic algorithm is presented. In the optimal trajectory planning, the joint angular velocity profiles are formulated using cubic polynomial with three parameters, and the fitness function to minimize the residual vibration of the payload of the two-link flexible robot arm is defined as a function of the four parameters. The optimal trajectory planning algorithm is constructed by use of the fitness function and the genetic algorithm. From the view point of the dynamics of the two-link flexible robot arm, the suitable search intervals of the genetic algorithm are discussed to effectively implement the optimal trajectory planning. Furthermore, the numerical calculations and experiments have been carried out, and it is confirmed that the residual vibrations can be remarkably reduced.
This paper describes a new method of detection and measurement of fingertip slip on the surface of a manipulated object in a multi-fingered precision manipulation with rolling contact. Due to the fact that slip sensors are still in a basic research phase and no slip sensor is compatible with the actual fingertip manipulation, our method is based on the multi-sensor fusion of vision, joint-encoders of the fingers, and finger-tip force/torque sensors. Position of the contact between the object and the fingertip is computed in realtime from the measured pose of the object and the fingertip position. Slip displacement of the fingertip contact is then separated from the displacement by rolling mo-tion of the fingertip. Reliability of the slip detection from the noisy data is improved using the tangential-to-normal ratio of the measured force at the contact and the mutual relationship between the tangential force and the direction of the contact displacement. Results of the experiments show the effectiveness of the method.