Sliding mode controllers (SMC) can achieve robustness against modeling errors and disturbances but they require upper-bounds of uncertain system dynamics. We proposed an adaptive robust sliding mode controller (ARSC-R) for robot manipulators elsewhere. It identifies both the system parameters and the upper-bounds of uncertain system dynamics. In this paper, we introduce a time-varying hyperplane into SMC and extend ARSC-R to a new controller named ARSC-M. This controller can achieve high control accuracy and good robustness. Our method is successfully applied to path control of a two-link robot manipulator.
This paper discusses a new sensing strategy for the Dynamic Active Antenna which can estimate the contact point between an insensitive flexible beam and an object by using multiple mode of natural frequencies of the beam in contact with the object. We first prove that the contact position is uniquely determined if we can consider every mode of natural frequencies of the beam in contact with the object. We also show that the use of the fundamental and the second order natural frequencies is sufficient for uniquely determining the contact point if the beam has uniform mass and stiffness distribution. The strategy is composed of two steps. In the first step, the fundamental and the second order natural frequencies of the beam in contact with the object are evaluated by utilizing a Maximum Entropy Method. Then by using the mapping diagram from those two frequencies into the contact point, we can obtain the contact point. Experimental results are also shown to verify our idea.
The Artificial Active Antenna is the sensor system motivated by the insect's antenna. It can detect the location between an insensitive flexible beam and an object through measurement of the rotational compliance on the beam in contact with the object. The goal of this paper is to consider the effects of the environment curvature on the sensing accuracy. We first introduce a set of basic equations representing force-deformation and geometrical relationships. Both numerical and approximate solutions are shown with experimental results. We show that the effect of the environment curvature on the sensing accuracy can be discussed by usung one non-dimensional parameter consisting of the pushing angle, the contact distance, and the radius of curvature of the object. Finally, we show that the environment curvature makes little influence on the sensing accuracy.
A vision and touch fusion method which utilizes actuator's motion in oiler to acquire an object position and orientation effectively is proposed. To determine actuator's motion, this method utilizes estimated errors of estimated values and the three-dimensional shape model of the object. After acquiring an image of the object, edges which should be sensed by a tactile sensor are determined. A method for acquiring camera-tactile sensor coordinates transformation in an active way is also proposed. These methods are examined in an experimental system.
In many kinds of industries, high speed robots are urgently required. In this paper, we propose an ultrahigh speed robot with 6 D. O. F. based on parallel wire mechanism. Because of low stiffness of wires, vibration problems arise in actuation. To overcome vibration probloms, internal forces among wires are effectively utilized. For this purpose, we analize the elasticity of wires and define two kinds of internal force stiffness. Basing on those results, we develop an ultrahigh speed robot FALCON-7 (FAst Load CONveyance Robot using seven wires) with six degrees of freedom. It is experimentally confirmed that the proposed robot attains to maximum speed 13[m/s] and the peak acceleration exceeds 40[G], even if considerably small D. C. motors (60[W]) are used.
Parallel mechanisms have advantages such as good force/torque output, high speed, and high accuracy. They can also manipulate the objects with soft links such as strings. Their limited workspace gives safety when the mechanism is used closely to human. Parallel mechanisms are suitable for robotic system for rehabilitation or assistance of the elderly people or the disabled people. Therefore, an upper limb motion assist system is proposed and being developed. This system aims at assisting people with upper limb disability to move the arm by his/her own will. Design strategy of the system is discussed at the first stage of the development, because it effects the motion range. In this paper, firstly a concept of the upper limb motion assist system is illustrated. Then, statics of the forearm motion with the proposed system is considered. An experiment is also carried out in order to determine a parameter included in statics. Finally, statics of the forearm and upper arm is considered and the relation between the design parameters of the system and the motion range of the arm is estimated using simulations.
An electrostatic motor technology that makes it possible to actuate machines with normal dimensions (not micro machines) by electrostatic force is developed. The novel motor is named AC Dual Excitation Multiphase Electrostatic Drive (ADEMED). It consists of a pair of two thin plastic films, called slider and stator, in both of which 3-phase parallel electrodes are embedded. By applying a 3-phase AC voltage to the electrodes in the two films, the slider film slides on the surface of the stator. A prototype of the motor is fabricated and tested. The prototype has a mass of 7 [g] and generates a thrust force and a power of 4.4 [N] and 1.6 [W] respectively. From these measured power and mass, the power/mass ratio of this motor is calculated as 230 [W/kg]. In terms of this performance, this motor exceeds the standard of typical mechatoronic servo motors reaching the highest level of AC servo motors that are commercially available.
This paper describes a method of tracking moving objects in a cluttered scene. If the motion of an object is similar to that of the background, the contour is not determined only by optical flow. It is also difficult to determine the contour only from edges because many edges may be extracted in the background and no edges may be extracted on some parts of the contour. But the contour is determined by using optical flow and edges in a long sequence. When an object motion is different from the neighborhood, the motion boundary is extracted as the contour. Some edges near the motion boundary are extracted and replace corresponding parts of the motion boundary. While the object is moving, more edges are added to the contour. When two objects with similar motion overlap, the contours are predicted by the stored contours and the current optical flow. The object boundary is determined by the edges near the predicted contours. Experimental results for synthetic and real scenes show the usefulness of the method.
In this paper, a new shape control law is proposed to bring a serial rigid link manipulator with hyper degrees of freedom into a specified curve. A shape control is one of the most fundamental controls for a hyper degrees of freedom manipulator. This control law is derived from the point of view of decreasing a certain energy function based on its dynamics. The concept of a homogeneously decentralized control scheme is also proposed for the practical application of the control law to the hyper degrees of freedom manipulator, and it is shown that the derived control law can be realized in a homogeneously decentralized control scheme. The effectiveness of this control law is verified by not only computer simulations but also hardware model experiments.
Although wheels are very efficient on flat and tight terrain locomotion, they cannot climb up stairs or even a step. Stairs or steps are the most popular obstacles in outside applications of mobile robots especially in artificial environments. This paper provides a new wheel-feet hybrid mechanism, named as Enhanced Wheel System (EWS), for rough terrain locomotion especially for climbing up stairs or a step. To climb up stairs or a step by the EWS, several ‘feet’ combined on each wheel (named as ‘wheel-feet’) are kept always horizontal by parallel link mechanisms controlled by the servo-mechanism. Some prototype machines with the EWS have been made to show that they are able to run smoothly on flat terrain by wheels and climb up and down stairs using those ‘feet’. In this paper, the authors describe a new prototype machine (EWS-4) with a carrier has been made to certify that the EWS can be used in actual use, carrying about 100[kg] of payload on a carrier. EWS-4 has 4 ‘wheel-feet’ with 4 ‘feet’ in each ‘wheel-feet’, and 4 wheels to run. The specifications of EWS-4 are that 1600[mm] long, 980[mm] wide, 950[mm] high, 1000[mm] of wheel base, 600[mm] of tread and about 200[kg] of weight. Experiments to climb up and down stairs of 150[mm] high and 350[mm] deep, were held successfully carrying about 70[kg] operator and control units.
This paper deals with a singular-point analysis of the locus for the two mobile robots traveling along a sinusoidal wavy road with carrying a long bar. The robots are assumed to be driven by crawler mechanism and to have a singlelink prismatic arm. The bar is also assumed to be kept horizental and at a given height and span. Modeling the two mobile robots by three-link mechanism, the locus of the two mobile robots are obtained in terms of their location-coordinates, which yields three kinds of singular points. At these singular points, the movement direction in each robot is analyzed, and obtained the movement direction rules at singular points, which should be a supplemental rules to those obtained in the previous report. Finally this paper has found the existence of the infinite loop, in which the two robots would move back and forth endlessly, and its existence condition is shown in terms of the height and span of the bar to be carried.
An optical wireless communication system has been expected as a method of data and command transmission for mobile robots. The problems of the optical wireless system are interruptions for light beam by the structures in the plant, and necessity of precise tracking control of the beam direction. We developed the system composed of two communication stations, which called relay station and mobile robot station having the same structure. The developed system has functions of acquiring the other station and tracking it each other, and the communication with a rate of 130[Mb/s] for the mobile robot has been performed. Moving speed of 2.5[km/h], communication distance range from 1.5[m] to 10[m], pitching and rolling of 2[Hz], frequency, and 10 [degree], amplitude, are permitted. These performances are proved by experiments using the stations made for experiment.
In this paper we propose the algorithm of collision-free trajectory generation which describes the joint trajectories of a manipulator by B-spline curves and optimizes the value of these control points using the Complex Method under full dynamic and kinematic constraints. The algorithm has the following advantages: (1) It is extremely concise and applicable to the problem of a multi-degrees of freedom manipulator with the complex constraints caused by obstacles, kinematics, and dynamics; (2) It can generate trajectories while taking the priority of the constraints into account; (3) Weighting factors of the performance indices corresponding to the constrains are computed automatically; (4) It needs less memory for storing the generated trajectories. Simulation results are also shown for the trajectory generation of a three degrees of freedom manipulator.
In this paper, trajectory control problem of the robot manipulator is considered. First, we briefly introduce robust stabilizing robust servo compensator design for linear uncertain systems, which is called IMPACT. Then we apply IMPACT to the problem in concern. It will be shown that the resulting system is internally stable and the tracking error will converge to zero, as is a natural consequence of the internal model principle. The compensator design is finally reduced to the so-called Nevanlinna-Pick's interpolation problem. The proposed method is highly robust to the parametric inaccuraries and the lack of structural information.
In this paper, we consider a virtual tennis as an application of virtual reality. In such an application, not only a visual display but also a force display is an important device. This device should have its large feasible area, high speed, high acceleration, force presentation to an operator and safety simultaneously. Then, we propose a new type force display system using a parallel wire drive mechanism. Because this force display has some advantages of its low inertia and simple structure, its good performance is expected. In this paper, we firstly specify details of the virtual tennis system, including an HMD (Head Mounted Display). Secondly, we describe a new method to investigate the feasible area of the proposed force display. Also, an easy procedure of calculating desired wire tension is proposed. Finally, we demonstrate some basic experimental results to verify performance of the proposed display.