This paper discusses a motion control of horizontal bar gymnast robot with two links and one passive joint on the bar. First, we show that the amplitude of the swing of the first link increases with resonance and parametric excitation by swinging the second link periodically. Next, we propose the control method using entrainment to produce each excitation by swinging the second link ‘in phase’ with the motion of the first link. In our method, the control input is consisted of periodic solution of van der Pol's equation inputted the angular velocity of the first link. Finally, we present experimental results that swing up control and continuous giant swings can be realized in the real robot.
This paper describes a method of realtime person tracking in a cluttered background by integrating optical flow and uniform brightness regions. Optical flow is extracted at points with enough contrast in an image. Assuming that the target person moves at a sufficiently large angle to the optical axis, the target can be detected in the image as a region where flow vectors are nearly uniform. Uniform brightness regions are extracted as connected points where optical flow cannot be obtained due to lack of contrast. At each frame, tracking is performed by continuously updating the flow and the uniform brightness regions of the target based on the prediction of those regions by using the target motion in the image. As long as, at least, one of these visual cues is effective to distinguished from the background and other objects, the target person can be tracked. Our proposed method was implemented on a realtime image processor with multiple DSPs and successfully tracked a target person in realtime.
We are studying an intelligent vision-based teleoperation system, which does several works around a telephone pole. This system has following two features for a low cost and a high reliability. One is that this system has several special exchangeable work modules, which have suitable structures for each work. The other is that we do not aim to realize a full automatic system but a half automatic one, that is occasionally supported by the operator. Moreover, a control software is based on GUI (Graphic User Interface) and easy for the operator to instruct the system intuitively. In this paper, we treat a work, where a metallic band is attached to a telephone pole, and describe a new band that has a new structure and is suitable for our teleoperation system, a new work module for attaching the band to the telephone pole, a basic configuration of the teleoperation system and a vision-based method for making the work module attached to a robot end-effector achieve a desired position of the telephone pole and attaching the band. We evaluated the precision of the positioning task by doing experiments of attaching the band repeatedly.
We propose a method for generating an assembly-task model from human demonstration. The model is pairs of operational coordinates and local contact-state transition models (local models) allocated in the coordinates. To generate the model, (1) the demonstrated data is segmented in each contact-state transition, (2) the segmented data is analyzed for setting operational coordinates using the component principal analysis, and (3) the local models are allocated to contact vertex pairs projected onto the operational coordinates. The usefulness of our method is discussed by the analysis results of demonstration in two assembly tasks and the robot task-execution using the generated models.
Modeling contact-state transitions is very troublesome. To deal with this problem, we have investigated a method of allocating local contact-state transition models (local models) to vertex pairs on which contact-state transitions occur and grouping the allocated local models according to a task process. In this paper, we propose a method of the allocation and the grouping from human demonstrations. Concretely, (i) for the allocation, vertex pairs where contact-state transitions occurred are found by using C-constrains in demonstrated data and (ii) the directions of contact-state transitions or the scope of the allocated local models are investigated for the grouping. We applied our method to some insertion tasks and tested it by performing the tasks by a compliance-controlled robot which had the generated groups of the local models. The experimental results showed the groups of local models work well as models of contact-state transition. As the result, we verified usefulness of our proposed method.
This paper proposes a realtime trajectory planning and control method of a robot arm for obstacle avoidance. If the distance between a link and a object are small, suggesting that a collision is about to occur, then an alternative trajectory is calculated to prevent the collision while minimizing the error in the desired (commanded) trajectory. The trajectory control algolithm that results in the form of a constrained minimization problem. Key to the trajectory modification algorithm is derivation of the Jacobian matrix relating changes in endeffector velocity to interference verocity. Simulation results demonstrate the performance of this algoritm and experimental results veryfy it's effectiveness.
Although an impedance control is one of the most effective control method for a manipulator in cntact with its environment, the end-effector of the manipulator does not move until an external force is exerted. In order to control the manipulator motion before contact with the environment, a non contact impedance control has been proposed, which can regulate not only the end-point impedance but also virtual impedance between the manipulator and the environment using visual information. The characteristics of the non-contact impedance control, however, is determined by the virtual impedance which must be designed according to given tasks. The present paper proposes a method to regulate the virtual impedance parameters using neural networks by reducing an energy function during iterative execution of the given task. The proposed method is implemented using a direct-drive robot in a planar task space to show effectiveness of the method.
This paper proposes the measurement principle of a sound source direction in the two-dimensional space. Such kind of differences like the transferring time, phase shift, and level of the sound wave are treated for the measurement in general. Our approach is to use the differences of sound levels by taking the advantage of the condenser microphone's simple sensitivity characteristics in directivity so that the direction is obtained by the simple signal processing. Basically the minimum number of the microphone set is three for the triangular arrangement. However, the set composed of four microphones for the orthogonal arrangement is treated for high accuracy. Formulation of the relations among the differences of the sound levels is shown. Also, the calculation procedure for determining the direction is extracted and experimental results are shown to verify the validity of the measurement.
This paper introduces an attitude control scheme based in optimal force distribution using quadratic programming which minimizes joint energy consumption. This method shares similarities with force distribution for multifingered hands, multiple coordinated manipulators and legged walking robots. In particular, an attitude control scheme was introduced inside the force distribution problem, and successfully implemented for control of the articulated body mobile robot KR-II. This is an actual mobile robot composed of cylindrical segments linked in series by prismatic joints and has a long snake-like appearance. These prismatic joints are force controlled so that each segment's vertical motion can automatically follow the terrain irregularities. An attitude control is necessary because this system acts like a system of wheeled inverted pendulum carts connected in series, being unstable by nature. The validity and effectiveness of the proposed method is verified by computer simulation and experiments with the real robot KR-II.
This paper is concerned with control of a 3 link planar underactuated manipulator that is known as a second order nonholonomic system. Since we have already proposed a control law that ensures convergence of its state to a desirable trajectory and to any desired final point, we propose a method of design of a desirable trajectory that starts from any given initial point, and then passes any given desired passing point, and finally converges at any given desired final point.
Humans can communicate each other by gestures. Even if they cannot recognize them at first, they can understand each other through interaction. This paper presents a robot system with such capability. The robot detects its user by recognizing his/her face. It can accept his/her commands given by gestures. The user may use unknown gestures to the robot. If the robot does not respond to his/her gesture, the user usually iterates the same gesture. The robot detects this repetitive pattern as an intentional gesture by which the user wants to give it some order. Then it shows a little action according to the meaning of the gesture that the robot guesses. It observes the user's reaction to its action. If he/she continues the same pattern gesture, the robot considers that its understanding is right, completing the action. It also registers the gesture pattern with the meaning. Otherwise, it iterates the same procedure taking another action as a candidate of the meaning. We have implemented such interactive capability on an intelligent wheelchair. It is convenient that we can make it come or go by gestures when we are off. Experimental results confirm that the proposed interaction method is useful in actual complex environments where even registered gestures cannot always be recognized.
Kyushu Electric Power Company has developed dual-armed mobile-robots for maintaining works in electric distribution systems. Though successful in reducing operator's demanding jobs, it still requires some human assistance. For automating some capabilities of this robot, we have developed a 3D object-localization method for robot's positional adjustment. The method is designed to be insensitive to noise and outliers. At the same time, run-time efficiency has also been considered. This paper reports this algorithm as well as its performance evaluation.
In this paper, we show a design method of an attitude controller for “Torque Unit Manipulator ( TUM ) ” proposed by us as a new type of space manipulator. TUM can be regarded as a kind of nonholonomic system. Therefore, it is difficult to design a controller. The point of this paper is the following. That is, using a special feature of TUM, we design a controller based on trajectory planning. We show the effectiveness of our method through simulation.