In this paper, we propose a method of trajectory planning for an object in pushing operation, which is to move the object on a floor to desired position and orientation using one arm. The feature of this method is that not only position and orientation of the object but also friction between the arm and the object are considered. We suppose that the distribution of magnitude of friction between the object and the floor is known. First, the state equation of the system and constraint equations about state and control variables are derived from kinematic constraints of the object. Then we make a performance index about distance, and translate the trajectory planning into an optimal control problem with state and input constraints. The trajectory of the object is obtained by solving the problem numerically. In the latter part of this paper, the trajectory planning is extended to that with obstacle avoidance. Numerical examples show the effectiveness of the proposed method.
Autonomous walking machines are generally required in dangerous situation in which humankind cannot step. Thus, walking machines have to return to the base position by themselves, even if a leg is injured by some accidents. In such a case, hexapod walking machine has advantages, because it can keep walking by remained five legs. This paper proposes a new gait rule named injury-adaptive wave gait. The new gait is available for not only normal hexapod walking, but also injured hexapod walking. Additionally, to apply the new gait rule smoothly, we propose a new control strategy for leg motion control. The strategy uses a notion of distributed control to realize synchronized motion among six legs. By combination of the gait rule and the control strategy, walking machine can realize suitable gait for its walking condition.
The problem of path planning is studied for the case of a mobile robot moving in the environment filled with obstacles whose shapes and positions are not known. The robot is assumed to know its own and the target's positions and to have a sensory feedback which provides it with local information on its environment. An aggressive algorithm is proposed using the space topology and convergence and target reachability of the algorithm are explained. Advantages of the algorithm are shown as compared with a number of existing algorithms. Finally, simulation results show effectiveness of the proposed algorithm.
This paper deals with two fundamental evaluation of characteristics of swarm intelligence in multi-robot system. One is related to swarm intelligence emerged as an ability of space coverage behavior. The other is that as an ability of solving a simple maze. In general, a certain ability emerged only in multi-robot system is called ‘swarm intelligence’ and the multi-robot system is expected to consist of many robots with simple mechanical function and small intelligence. With respect to space coverage behavior generated by many robots equipped with locomotion function and obstacle avoidance intelligence, we investigate the characteristics of space coverage ratio with respect to two parameters; one is population size of multi-robot system and the other is diameter size of a single robot. We show that the effect of population size on the space coverage behavior is greater than the ratio of the population size increase, and that the effect of robot diameter is minor in the case of large population size of multi-robot system. In using the multi-robot system for the task to find the route in simple maze the multi-robot system can solve simple maze problem and we evaluate the ability of accomplishment of the task.
Locus ripples in the motion controlled mechatronic servo systems is discussed. The contour control of the mecha-tronic systems such as industrial robots and machine tools is generally implemented in a way such that an objective trajectory with a desired velocity is divided into small segments of the reference input time interval and actuators of the servo motors are controlled to pursue the divided segments. The relation between the reference input time interval and the locus ripples in the mechatronic systems were derived by using the first order model of the system and validated based on experimental results of an DC servo motor.
In this paper, we propose to apply an on-line planning method for a desired signal to robot manipulators. On-line planning has the advantage of off-line planning in the following point. In off-line planning, a servo system reduces the influence of initial state variables, disturbance and parameter perturbation. In on-line planning, however, both the planning of the desired signal and the servo system can reduce the influence. That is, the influence can be reduced by changing the desired signal within its permitted domain. In the on-line planning, the permitted domain of the desired signal is expressed as parameters of the desired signal. This means that, the planning of the desired signal and design of the control system are replaced by the design for the controlled object having the restriction of the desired signal. This method has the following advantages: (1) Many methods for the design of the control system can be applied to the planning for the desrired signal (2) Processing time can be short enough for the on-line planning (3) It is possible to consider the stability of the whole system with the planner and the control system (4) Planning for desired signal includes both path planning and trajectory planning.
In recent years, demands for advanced sensing in robot tasks using multiple sensing modules have been increased. In robot vision tasks, distributed use of multiple cameras is required to overcome limitations of a narrow field-of-view and low 3D resolution when using a single camera. If a target object moves outside the field-of-view of a camera, we need to automatically switch the tracking task from the camera to another module. Integration of multiple sensing information is also an important issue. A traditional approach for construction of such system is to organize the modules with a single and centrally controlled system. However, this approach has disadvantages in various aspects: flexibility, robustness, extendability, and efficiency in achieving tasks. To overcome these difficulties, decentralized and cooperative control of multi-robot is a promising approach. In this paper, we propose a concept of decentralized and cooperative sensing system for robot vision tasks. We present a prototype of such visual sensing system implemented using a real multi-robot system. It performs visual inspection of water leakage on a sleeve of a valve. A novel feature of the system is it consists of 3D model-based agents which communicate 3D model information of the task environment for distributed sensor planning.
Robot engineering is developed mainly in the field of intelligibility such as in a manipulation. Considering the wide use of robots in the future, the robots should be studied from a viewpoint of saving energy because a robot is a kind of machine with an energy conversion. This paper deals with minimizing the energy consumption of a manipulator which is driven in a point-to-point control method. When the links of a manipulator are decelerated for positioning, the motors at the joints generate electric power. Since this energy can be regenerated to the source by using a chopper, the energy consumption of a manipulator is only by the heat loss of the electric and the frictional resistances. The minimization of the sum of these losses is reduced to a two-point boundary-value-problem of a nonlinear differential equation. The solutions of the equations are obtained by the generalized Newton-Raphson method. In this case the starting function for an optimal solution is selected from a view point of saving energy. It is seen from simulations that the second link of a two-link manipulator should be rotated backward in a certain condition.
This paper develops a new methodology of Combined Passive/Active Suspension System for the 3D micro-gravity simulation, and demonstrates its validity with a prototype test bed. The system is a combination of low-impedance passive suspension, which is transparent to the high frequency dynamics, and tribial servo-tracking control which covers global motion of the system. The prototype shows a good performance for 3D dynamics hardware simulation such as impact, collision, or docking of space systems.
An assembly task-oriented manipulation system (ATOMS) is proposed that monitors the changes in task process and switches task strategy accordingly. The system is divided into five functional blocks: task description, motion planning, motion execution, motion monitoring, and robot control. The assembly process is described as a series of discrete contact states and the task is programmed as sequence of motions connecting the current contact state to the next desired one. During task execution, the motion can be switched in realtime if a contact-state transition is detected. The An experimental manipulation system was developed based on the concept of ATOMS. It has a fourlayer structure, a 6-DOF direct-drive manipulator and a multi-processor, multi-task controller based on a transputer. In the second layer, a motion monitoring and evaluation (MME) module, in which the proposed detection algorithm is installed, and a motion execution management (MEM) module are simultaneously executed. The result for a square peg insertion task, programmed with a few primitive motions, in which different types of contact-state transitions occur and a position (orientation) error is introduced in the task environment, demonstrate that not only is the concept of ATOMS effective, but also that a manipulation system has the ability to execute assembly tasks with high reliability.
Dynamic control is one of the methods which enable quick and accurate motion of robot arms. However, this method has been rarely applied to industrial robots. One reason is that dynamic control has been difficult to be performed real time by using presently available processors since it requires huge amount of computation. Described in this paper is an optimizing compiler which can automatically generate an efficient program for dynamic control computation of robot arms. Source program, which can be developed with an algebraic computation system like REDUCE, is given as symbolic equations. The optimizing compiler transforms the equations into a set of statements which has a possible simple form of computation. The method is based on the factorization algorithms proposed by authors. After that, the optimized statements are encoded by C Language and arranged for an object program. The optimizing compiler is designed according to an object oriented approach. The effectiveness of the optimizing compiler is also shown through experiments.
This paper describes an experimental result of motion of a space robot using a drop shaft. The drop shaft is 710[m] deep and can be used for micro-gravity experiment during 10 seconds. The robot for this experiment equipped with three links. The micro-gravity environment had 0.03[m/s2] variation. When the robot was apart from the holding mechanism, it obtained small linear and angular momentum. However, the robot did not collide with the environment during the motion. A simulation was conducted and compared with the experiment. The z-axis rotational motions are in good agreement with each other, however the x and y-axes, which are parallel to the vision plane, were not. The robot got no damage during the experiment.
To develop the three dimensional instruction input device for robots, a spherical device rotatable on each three axes was formed and experimented by using three magnetic resistance elements and three moving magnet series. It was confirmed that the device can detect rotational amount and direction for the longitudinal (back and forth) motion of the magnet series on each three axes, but there exists no interfering signals from the cross-sectional rotation. So it suggests that the device can be expanded into a real three dimensional one.