In this paper the role that shear deformation effect plays in flexible manipulator dynamics is investigated and reported. The shear deformation effect of manipulators with three typical cross-sectional geometries, namely, hollow round, hollow square, and hollow rectangle, is studied. In addition, one important issue for manipulator design considerations regarding the influence of the link dimension variations on flexible dynamics is also investigated. The dynamic simulation results show that the shear deformation effect is approximately inverse proportional to the thickness of manipulator link regardless of cross-sectional shapes, if the link length is fixed. It can also be observed that the longer the manipulator link the less shear effect will influence the manipulator deflection, although the frequency of deflection variances becomes less. Based on the simulation results, it is suggested that hollow circular cross-sectional link should be adopted to reduce shear effect for short and thin manipulator links as far as the flexible linkage manipulator design is concerned. For hollow square and hollow rectangular link cross-sections, the manipulator link must be long and thick to avoid significant influences of shear effects.

A novel off-line technique for automatic calibration of kinematic parameters for hydraulic manipulators is presented. Hydraulically actuated manipulators have joints which are always powered and, unlike conventional robots, may not have conventional joint sensors to exploit in the calibration procedure. Instead, our approach employs an external three-dimensional linkage, termed “the calibrator”, which has sufficient number of joints with corresponding sensors. One end of the calibrator is grasped by the manipulator's end effector while the other end is attached to a passive spherical joint fixed to the world coordinate system. The mobile closed kinematic chain thus formed has the added advantage of eliminating the explicit measurement of the manipulator's endpoint location. A sequential identification technique that uses a least squares numerical search algorithm has been developed based on link-by-link movement of the manipulator. Simulation and experimental calibration results on a typical mobile hydraulic manipulator are reported in this paper, which show that the proposed technique is globally stable, and potentially fast, inexpensive, and easy to apply on site.

We have designed, built, and tested a new wheel control system for the HERMIES-III robot. HERMIES-III is a large mobile robot with omnidirectional steering that is designed for human scale experiments. During each cycle (at 20 Hz), the wheel control system moves the robot toward a goal and calculates the current position of the robot. The system has seven modes for moving to a goal and the goal may be changed during motion of the robot.

Motor torque constant is an important parameter in modeling and controlling a robot axis. In practice this parameter can vary considerably from the manufacturer's specification, if available, and this makes it desirable to characterise individual motors. Traditional techniques require that the motor can be removed from the robot for testing, or that an elaborate technique involving weights and pulleys be employed. This paper describes a novel method for measuring the torque constant of robot servo motors in situ and is based on the equivalence of motor torque and back EMF constants. It requires a very simple experimental procedure, utilizes existing axis position sensors, and eliminates effects due to static friction and joint cross coupling. A straightforward extension to this approach can provide a measurement of motor armature impedance. Experimental results obtained for a Puma 560 are discussed and compared with other published results.

This paper presents a framework for the design of a hierarchical Simulator of a robotized sequential technological process. The framework employs concepts of discrerte event simulation modelling. The Simulator consists of two layers: the Simulator of a robot and technological process, and the interpreter and planner of robot tasks. A format specification of both layers is presented. The proposed simulation approach is expected to result in significant improvements in the robot task plan generation and in higher efficiency of a technological process.

This paper treats, in a general way, the problem of mobile robot navigation in a totally unknown environment. The different aspects of this problem are dealt with one by one. We begin by introducing a simple method for perceiving and analyzing the robot's local environment based on a limited amount of distance information. Using this analysis as our base, we present a navigation algorithm containing different action modules; some of these actions use Fuzzy Logic. The results presented whether experimental or simulation show that our method is well adapted to this type of problem.