摘要:

AbstractThis article describes the design and control of a two‐joint, two‐link flexible arm. This flexible arm was built with very light links, has most of its mass concentrated at the tip and uses a special mechanical configuration to approximately decouple radial tip motions from angular tip motions. The lightweight design and decoupling maximize the efficiency of power transmitted to the load. An important problem when controlling lightweight flexible arms is the large Coulomb friction of the motors. A two‐nested‐loop multivariable controller is used to control the lightweight flexible arm with friction in the joints. The inner loop controls the position of the motors while the outer loop controls the tip position. The resolved acceleration method is generalized to control this flexible arm. The compliance matrix is used to model the oscillations of the structure and is included in the decoupling/linearizing term of this controller. Experimental results are presented. ©1995 John Wiley&S

ISSN:0741-2223    

DOI:10.1002/rob.4620120102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this article, three models in two different spaces are compared for use with an image processing system working in real time. A static geometric model of a robot work‐cell is held in computer memory as several solid polyhedra. This model is updated as new objects enter or leave the workplace. Similar 2‐D slices in joint space, spheres, and simple polyhedra are used to model these objects. The three models are compared for their ability to be updated with new information and for the efficiency of the whole system in accessing data concerning new objects. The system supplies data to a “Path Planner.” The path planner contains a geometric model of the static environment and a robot. The robot machinery structure is modeled as connected cylinders and spheres and the range of motion is quantized. ©1995 John Wiley&S

ISSN:0741-2223    

DOI:10.1002/rob.4620120103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis article addresses the problem of base placement for mobile robots using a reachability analysis. A simple geometric solution is proposed to determine the appropriate base locations from which the robot can reach a stationary or moving target point. This leads to a simple criterion for automated base placement, thus relieving the operator from the tedious and repetitive procedure for continuously positioning the robot base manually during the execution of the end‐effector task. For robots with one degree‐of‐mobility such as tracked robots, the feasible base locations consists of a region on the translational axis, the boundaries of which are derived in this article. The results are used to obtain the base locations so that the robot can reach a vertical line, a square surface, and a cubic volume. Using the proposed method, two experimental studies at the JPL Surface Inspection Laboratory are described: scanning a surface and reaching inside an opening. The results of the article are extended to mobile robots with two and three degrees‐of‐mobility such as rover‐mounted arms and gantry robots, and a simple numerical example is given for illustration. ©1995 John Wil

ISSN:0741-2223    

DOI:10.1002/rob.4620120104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAn experimental investigation on the control performances of a single‐link flexible manipulator fabricated from composite laminates is presented. The dynamic modeling of the flexible manipulator is accomplished by employing Hamilton's principle, prior to developing a finite element formulation. An output feedback controller associated with two collocated angular position and velocity sensors is designed and experimentally implemented. Comparative works are undertaken to demonstrate some of the advantages to be accrued from this proposed methodology. It is shown that the manipulator fabricated from composite laminates has superior performance characteristics, such as smaller tip deflections and a smaller input torque relative to the manipulator fabricated from aluminum. ©1995 John Wiley&Sons, I

ISSN:0741-2223    

DOI:10.1002/rob.4620120105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis article focuses on finding optimal kinematic postures for two robot arms performing various assembly tasks without the aid of jigs and fixtures. The goal of the work is to identify the manipulator postures that would result in some optimum kinematic conditions for initiating a typical male‐female assembly. Specifically, the article addresses issues related to the following question: In the absence of preset jigs and fixtures, where are the optimum location in the 3‐dimensional work space and the optimum orientations of the assembly parts (therefore, the postures of the manipulators holding the parts) to perform a fixtureless assembly? First, using velocity and force ellipsoids a performance criterion is developed for the optimal kinematic posture based on constraints that are imposed by the kinematic coupling of the two robot arms as well as the environment. Next, an algorithm based on a null‐space search technique is formulated to “search” for the posture of the two‐arm system that maximizes the performance criterion within the set of postures that satisfy given constraints. Finally, the algorithm is demonstrated numerically for two planar robots performing typical fixtureless assembly operations. ©1995 John Wil

ISSN:0741-2223    

DOI:10.1002/rob.4620120106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this article, we study the contact instability problem encountered in robotic manipulators while trying to make contact with an environment, such as grasping or pushing against objects, and propose a unified control strategy capable of achieving a stable contact against both stiff and compliant environments. The problem has three distinct stages of the contact task. In the first stage, free‐space motion, the robot is approaching the environment; in the second stage, post‐contact force regulation; in the third, impact stage, the transition from the first stage to the second. We make an experimental comparison of the control schemes that may be used for the three stages. For example, during impact, the manipulator should not lose contact with the environment, nor exert high impulsive forces on the environment, and in the post‐impact phase, the robot should have a fast force trajectory tracking. The best strategies for the above stages are experimentally determined and then combined into a single unified controller that can achieve stable contact as well as a fast force trajectory tracking response for surfaces of variable stiffnesses. This control scheme does not require a priori knowledge of the stiffness of the environment, and is able to estimate the environmental stiffness and tune gains accordingly so as to achieve the best response. Also experimentally compared is the use of such a scheme with impedance control, another method proposed in the literature for robotic contact task control. ©1995 John Wiley&Son

ISSN:0741-2223    

DOI:10.1002/rob.4620120107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0741-2223    

DOI:10.1002/rob.4620120101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY