A range finder system which is able to measure with high accuracy and at high speed has been developed. The performance is achieved with a special optical system and a pre-processing circuit. This system has 15 light stripes generated by a series of laser diode and cylindrical lens and the stripes are rotated by a galvanometric motor controlled mirror. This configuration also gives the system flexibility for sampling measurement density and high efficiency of available optical power of light sources. A pre-processing circuit extracts at video rate two dimensional coordinates of reflected light in TV image. Sub-pixel accuracy is achieved with a determination scheme using center of gravity calculation of the intensity profile. The system components (the optical unit, the pre-processing circuit, light pattern decoding and three-dimensional coordinates computing) are driven in a pipeline manner, which also contributes to the high speed measurement.
This paper presents a rigorous mathematical formulation for evaluating error behaviors and reliabilities in the computation of vanishing points for sensing 3-D from images. First, an optimal vanishing point estimation scheme is constructed by adopting a simple statistical model which assumes that image errors result from edge fitting in digital images. Then, reliability of thus computed optimal, estimate is theoretically evaluated, and the confidence level of the estimate is statistically deduced in quantitative terms. Finally, a simple scheme of calibrating the camera focal length is constructed in such a way that the reliability of the computation is maximized.
This paper proposes two items: One is a sliding mode based on a new concept concerned with redundancy. The other is a control scheme based on that concept for a redundant manipulator in space to grasp a floating object. The previously published methods required many calculations becasuse of using pseudo inverse. To deal with this problem, we introduce a new concept of redundancy based on redundancy of sliding mode itself, and introduce a new sliding mode. This concept is combined with a conventional sliding mode control method. By using this hybrid control scheme the number of calculations is reduced to about 1/5 or 1/6 for tracking the same trajectory of an end-effector utilizing the redundancy as that of the conventional methods. And the proposed control method eliminates the necessity of the estimation of uncertain motion parameters of translational and rotational momenta by adaptive gains. Finally the effectiveness of the proposed method is verified by computer simulations for the trajectry control where the satellite angular velocity is surpressed by taking advantage of redundancy based on a new concept.
The computed torque method has been regarded as a typical one for the control of manipulators. This method, however, not only requires a tremendously complicated calculation but also cannot avoid the performance degradation due to various parameter changes. This paper proposes the decoupling control method by applying the two degrees of freedom robust servo system to each axis, with which not only the interference forces but also system parameter variations can be strongly suppressed. By using this as the each axis position controller, the trajectory control only by using position command can be realized, and hence algorithm and calculation cost become very simple. Besides, almost all sorts of control system, that is impedance control, compliance control, force control, and hybrid control can be systematically and easily realized based on the trajectory control system. All the control systems proposed here are implemented centered about DSP and successfully experi-mented through the life-size six-axis manipulator.
The constraint condition for motion of objects in contact must be derived and analyzed for the sensing, control and planning of it. Assuming that a polyhedron moves in contact with another polyhedron and that no friction exists between them, the condition can be represented by homogeneous linear inequalities. In this paper, the inequalities is analyzed from the viewpoint of the complexity of the algorithm for solving it. Applying the singular value decomposition to the coefficient matrix of the inequalities and introducing an intersecting hyperplane, it is shown that the problem is equivalent to finding the intersection of half spaces or the convex hull of a set of points. The singular value decomposition enables us to find the solution in the minimal dimensional space, where the complexity of the algorithm is also minimal. A new algorithm is also proposed which is not optimal as asymptotic complexity, but significantly fast in the practical cases and independent of the dimension of the space. The algorithm is applied to the departure motion planning, and it is also shown that the basis of nonnegative linear combination, which is the solution of the inequalities, become the minimal number of direction for the searching.
For the teleoperation of force controlled space robots in orbit by a human operator on the ground, communication time delay becomes a difficult problem. In this paper, to solve this problem, a new teleoperation control scheme is proposed. In this scheme, the robot has two control modes: velocity and force control modes, either of which is selected automatically according to contact conditions between the robot and its environments. The coefficient that converts the force command into the velocity command is decided based on the analysis of the optimal approach velocity. Since the both control modes are implemented by an on-board computer in orbit, no force reflection to the human operator is needed even in the force control mode. Moreover, to aid the operator's 3 D visual perception, it is proposed to use a virtual beam which is generated by a ground computer using a geometrical model. With this aid, operation in the velocity control mode is improved.
Self-posture changeability (SPC), which is the characteristics that a link system changes its posture with keeping contact between link system and environment, is discussed for a general 3 D link system. Assuming that link system moves slow enough to suppress any dynamic effects, we first define the (ω0, ω) -posture changeability which is the characteristic that a link system has posture changeability for every force within a cone having the direction of ω0 and the solid angle of ω. The necessary and sufficient condition leading to (ω0, ω) -posture changeability is examined with the joint role assignments, namely, selection of compliant joint and position-controlled joint. Linking (ω0, ω) -posture changeability with physical parameters expressing friction cone, we also show a sufficient condition to realize self-posture changeability under the condition that contact point moves continuously over an object and no contact-point-jump appears. Finally, basic behaviors of SPC were confirmed by simulation using a simple 3 D link system and a sphere.
A pace gait considering in this study is the walking in which lateral legs form pairs and the members of a pair strike the floor in unison and they leave the floor in unison. In order to realize a stable pace gait, it is very important to control actively a walking cycle. Namely, the proper control of the walking cycle ensures the cooperation of the sagittal motion and the lateral motion. In this study, a control method of the walking cycle based on the motion control in the lateral plane is proposed. A discrete-time model is suitable for the analysis of the walking system in case off adjusting the walking cycle. By using the proposed discrete-time model, several control method of the walking cycle are discussed. At first, a conventional proportional plus integral control is examined by using a maximum absolute value of the closed loop eigenvalues as a performnce index. Secondly, an optimal servo controller and a dead beat controller are discussed. For the sagittal motion control, a trafectory of the leg is designed under the consideration of the algorithm of the lateral motion control. The COLT-3 achieved a smooth pace gait at a speed of 0.25 m/s.