In this paper, we present MIL (Multi-Information Local) map which is available for efficient navigation of a mobile robot in a known environment. A MIL map is equipped with procedures for checking a self-location at critical points in the environment, such as corners or intersections. This map also has information about the movement style between each location check point, such as following a wall. A mobile robot can move to the destination efficiently because a robot can estimate its self-location at each location check point by only executing procedures written in a MIL map, and can move between location check points by obeying the movement style written in a MIL map. A MIL map is created interactively from stereo images taken at location check points before autonomous movement. We have implemented a visual navigation system using a MIL map on a mobile robot. Experimental results have shown the usefulness of a MIL map.
This paper presents a basic formulation of motion dynamics of free-floating link systems, to establish a basis of the collision dynamics. The authors propose a new concept named “Extended Inversed Inertia Tensor (Ex-IIT) ”, which is an extended version of the IIT for ground-based arms, and discuss the virtual mass concept. By means of the concepts, they formulate the collision problem focusing on a velocity relationship just before and after the collision without sensing the impact force, but considering the momentum conservation law. The validity of the formulation is confirmed by a simple free-floating experiment.
In this paper, a method is proposed whereby both contact force exerted by a flexible manipulator and position of end-effector while in contact with a surface are controlled. The elastic deformations of the flexible links are approximated by means of B-spline functions. Then, the dynamic equations of joint angles, vibration of the flexible links, and contact force are derived. A controller for the dynamic hybrid position/force control of the flexible manipulator is designed on the basis of the singular perturbation method. A set of experiments for the dynamic hybrid control of the flexible manipulator using a force sensor has been carried out. Several experimental results are shown.
A new approach to detect contact points accurately during manipulation is presented. This approach applies motor algebra to unified processing for detection. First, an expression of sensory information using motor algebra and elementary operations of motors are discussed. Force, velocity and the normal vector of the tool surface are effectively combined using motor algebra. Second, using force/moment motors and geometric model of the tool, 1-point contact detecting scheme is formulated. Then, the velocity conditions at the contact point are clarified in relation to normal motors of the tool surface. Moreover a high-speed method of judging whether those conditions are satisfied is proposed introducing SVF (Surface Velocity condition Function) which is composed of the velocity motor and the normal motor at the tool surface. Finally, a linear evaluation function is defined to utilize force and velocity information complementarily. Experimental results show that the detection accuracy can be significantly improved using the evaluation function.
When a robot hits an object by a hammer, the robot manipulator has to absorb a impulsive reaction with the motor of a joint or a link. This paper deals with a flexible link for a hammering robot. When the root of the link is driven by a motor, the head of a hammer vibrates complicatedly because the litik is a distributed parameter system. The first mode of the vibration is of great use for increasing a hitting velocity and for absorbing a reaction from the object easily. The second mode or more, however, disturbs the hitting velocity and direction which is specified by an operator. In order to suppress the higher modes of the vibration, a hammer driving system is equipped with a feedback loop which is composed of a strain meter and a high pass filter. It is shown that the hammer system can hit an object from a normal direction with a specified velocity.
Environments where a robot executes a task are not always the same as the environment where the robot learned the task. Traditional teaching playback robots execute a task by replaying the learning trajectory. Therefore such robots can only be used in environments where location and shape of objects are always the same. Furthermore, such robots are required to learn every movement from the biginning whenever the operator gives a new task. To reduce this inconvenience, a robust form of task description that is adaptable in different environments is needed. This paper discusses a method of describing a task robustly, and also presents algorithms (1) to interprete the learning motion to a task description, (2) to modify the description to the task environment, and (3) to generate the task motion from the modified description. The system architecture using this description is also discussed. The system consists of a teaching interface, a task interpreter, a sensor module, a task planner, and a manipulator module. We installed these modules in a simple system. This achieved a good performance in a block assembly task although it was taught in a different environment.
The new method of hybrid control which is not based on orthogonal compliment has been developed. The motion of a rigid body can be expressed by genaral coordinates whose basis is composed of screws (motors) . The determination of generalized forces is exactly the same as the determination of the joint torque/force of the mechanism having the jacobian composed of the elements of the basis of the general coordinates. That is, the motion generated by the hybrid control is equivalent to that of the mechanism modeled by the basis. Using the mechanical model suitable to demanded tasks, this control strategy can be used in wide range of applications. The conventional hybrid control based on the concept of orthogonal compliment is considered to be the very special case of this method.
We constructed a one-link robot hand by using a pair of Rubbertuators. Because of hysteresis and nonlinearity of Rubbertuator, it is too hard to formulate an accurate model. So, we tried to apply the sliding mode theory to control the Rubbertuator-driven mechanism. The sliding mode controll for continuous system have been studied well, but a digital version is required for practical applications. We confirmed the validity of the digital sliding mode control, through experiments, by using it to control the Rubbertuator-driven mechanism.
Generally, a hybrid control is realized by sensor signal feedback of position and force. However, some robot manipulators do not have a force sensor due to the environment of robot manipulator. Moreover, a precise force sensor is very expensive. In order to overcome these problems, this paper proposes the estimation system of reaction force without using a force sensor. This force estimation system consists of the torque observer and the inverse dynamics calculation. Using both this force estimation system and H∞ acceleration controller, this paper realizes the hybrid control of position and force without force sensor. H∞ acceleration controller is based on H∞ control theory, and it takes account of the frequency characteristics of both sensor noise effect and disturbance rejection. The experimental results in this paper illustrate the fine hybrid control of the tested three-degrees-of-freedom DD robot manipulator without force sensor.
This paper presents an approcah for understanding a spatial structure from a wireframe model which have been constructed by a mobile robot with stereo system. We discover the object surface using relations of line connection and the basic geometrical knowledge of the 3-D world. The method can also infer unobtained lines, thus the occuluded surfaces can be alsoreconstructed.