29,052 research outputs found
Local position control: A new concept for control of manipulators
Resolved motion rate control is currently one of the most frequently used methods of manipulator control. It is currently used in the Space Shuttle remote manipulator system (RMS) and in prosthetic devices. Position control is predominately used in locating the end-effector of an industrial manipulator along a path with prescribed timing. In industrial applications, resolved motion rate control is inappropriate since position error accumulates. This is due to velocity being the control variable. In some applications this property is an advantage rather than a disadvantage. It may be more important for motion to end as soon as the input command is removed rather than reduce the position error to zero. Local position control is a new concept for manipulator control which retains the important properties of resolved motion rate control, but reduces the drift. Local position control can be considered to be a generalization of resolved position and resolved rate control. It places both control schemes on a common mathematical basis
Multiple configuration shell-core structured robotic manipulator with interchangeable mechatronic joints : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Engineering in Mechatronics at Massey University, Turitea Campus, Palmerston North, New Zealand
With the increase of robotic technology utilised throughout industry, the need for skilled
labour in this area has increased also. As a result, education dealing with robotics has
grown at both the high-school and tertiary educational level. Despite the range of
pedagogical robots currently on the market, there seems to be a low variety of these
systems specifically related to the types of robotic manipulator arms popular for industrial
applications. Furthermore, a fixed-arm system is limited to only serve as an educational
supplement for that specific configuration and therefore cannot demonstrate more than
one of the numerous industrial-type robotic arms.
The Shell-Core structured robotic manipulator concept has been proposed to improve the
quality and variety of available pedagogical robotic arm systems on the market. This is
achieved by the reconfigurable nature of the concept, which incorporates shell and core
structural units to make the construction of at least 5 mainstream industrial arms
possible. The platform will be suitable, but not limited to use within the educational
robotics industry at high-school and higher educational levels and may appeal to
hobbyists.
Later dubbed SMILE (Smart Manipulator with Interchangeable Links and Effectors), the
system utilises core units to provide either rotational or linear actuation in a single plane.
A variety of shell units are then implemented as the body of the robotic arm, serving as
appropriate offsets to achieve the required configuration. A prototype consisting of a
limited number of ‘building blocks’ was developed for proof-of-concept, found capable of
achieving several of the proposed configurations.
The outcome of this research is encouraging, with a Massey patent search confirming the
unique features of the proposed concept. The prototype system is an economic, easy to
implement, plug and play, and multiple-configuration robotic manipulator, suitable for
various applications
Parameter identification for a robotic manipulator arm
The development is described of a nonlinear dynamic model for large oscillations of a robotic manipulator arm about a single joint. Optimization routines are formulated and implemented for the identification of electrical and physical parameters from dynamic data taken from an industrial robot arm. Special attention is given to the role of sensitivity in the formulation of robust models of this motion. The importance of actuator effects in the reduction of sensitivity is established and used to develop an electromechanical model of the manipulator system
Resolved rate and torque control schemes for large scale space based kinematically redundant manipulators
Resolved rate control of kinematically redundant ground based manipulators is a challenging problem. The structural, actuator, and control loop frequency characteristics of industrial grade robots generally allow operation with resolved rate control; a rate command is achievable with good accuracy. However, space based manipulators are different, typically have less structural stiffness, more motor and joint friction, and lower control loop cycle frequencies. These undesirable characteristics present a considerable Point of Resolution (POR) control problem for space based, kinematically redundant manipulators for the following reason: a kinematically redundant manipulator requires an arbitrary constraint to solve for the joint rate commands. A space manipulator will not respond to joint rate commands because of these characteristics. A space based manipulator simulation, including free end rigid body dynamics, motor dynamics, motor striction/friction, gearbox backlash, joint striction/friction, and Space Station Remote Manipulator System type configuration parameters, is used to evaluate the performance of a documented resolved rate control law. Alternate schemes which include torque control are also evaluated
Gain scheduling for hybrid force/velocity control in contour tracking task
In this paper a gain scheduling approach is proposed for the hybrid force/velocity control of an industrial manipulator employed for the contour tracking of objects of unknown shape. The methodology allows to cope with the configuration dependent dynamics of the manipulator during a constrained motion and therefore a significant improvement of the performance results. Experimental results obtained with an industrial SCARA manipulator demonstrate the effectiveness of the technique
Industry-oriented Performance Measures for Design of Robot Calibration Experiment
The paper focuses on the accuracy improvement of geometric and elasto-static
calibration of industrial robots. It proposes industry-oriented performance
measures for the calibration experiment design. They are based on the concept
of manipulator test-pose and referred to the end-effector location accuracy
after application of the error compensation algorithm, which implements the
identified parameters. This approach allows the users to define optimal
measurement configurations for robot calibration for given work piece location
and machining forces/torques. These performance measures are suitable for
comparing the calibration plans for both simple and complex trajectories to be
performed. The advantages of the developed techniques are illustrated by an
example that deals with machining using robotic manipulator
A complete analytical solution for the inverse instantaneous kinematics of a spherical-revolute-spherical (7R) redundant manipulator
Using a method based upon resolving joint velocities using reciprocal screw quantities, compact analytical expressions are generated for the inverse solution of the joint rates of a seven revolute (spherical-revolute-spherical) manipulator. The method uses a sequential decomposition of screw coordinates to identify reciprocal screw quantities used in the resolution of a particular joint rate solution, and also to identify a Jacobian null-space basis used for the direct solution of optimal joint rates. The results of the screw decomposition are used to study special configurations of the manipulator, generating expressions for the inverse velocity solution for all non-singular configurations of the manipulator, and identifying singular configurations and their characteristics. Two functions are therefore served: a new general method for the solution of the inverse velocity problem is presented; and complete analytical expressions are derived for the resolution of the joint rates of a seven degree of freedom manipulator useful for telerobotic and industrial robotic application
Parameter identification and sensitivity analysis for a robotic manipulator arm
The development of a nonlinear dynamic model for large oscillations of a robotic manipulator arm about a single joint is described. Optimization routines are formulated and implemented for the identification of electrical and physical parameters from dynamic data taken from an industrial robot arm. Special attention is given to difficulties caused by the large sensitivity of the model with respect to unknown parameters. Performance of the parameter identification algorithm is improved by choosing a control input that allows actuator emf to be included in an electro-mechanical model of the manipulator system
Nonlinear Discrete Observer for Flexibility Compensation of Industrial Robots
This paper demonstrates the solutions of digital observer implementation for industrial applications. A nonlinear high-gain discrete observer is proposed to compensate the tracking error due to the flexibility of robot manipulators. The proposed discrete observer is obtained by using Euler approximate discretization of the continuous observer. A series of experimental validations have been carried out on a 6 DOF industrial manipulator during a Friction Stir Welding process. The results showed good performance of discrete observer and the observer based compensation has succeed to correct the positioning error in real-time implementation.ANR COROUSS
Design of Calibration Experiments for Identification of Manipulator Elastostatic Parameters
The paper is devoted to the elastostatic calibration of industrial robots,
which is used for precise machining of large-dimensional parts made of
composite materials. In this technological process, the interaction between the
robot and the workpiece causes essential elastic deflections of the manipulator
components that should be compensated by the robot controller using relevant
elastostatic model of this mechanism. To estimate parameters of this model, an
advanced calibration technique is applied that is based on the non-linear
experiment design theory, which is adopted for this particular application. In
contrast to previous works, it is proposed a concept of the user-defined
test-pose, which is used to evaluate the calibration experiments quality. In
the frame of this concept, the related optimization problem is defined and
numerical routines are developed, which allow generating optimal set of
manipulator configurations and corresponding forces/torques for a given number
of the calibration experiments. Some specific kinematic constraints are also
taken into account, which insure feasibility of calibration experiments for the
obtained configurations and allow avoiding collision between the robotic
manipulator and the measurement equipment. The efficiency of the developed
technique is illustrated by an application example that deals with elastostatic
calibration of the serial manipulator used for robot-based machining.Comment: arXiv admin note: substantial text overlap with arXiv:1211.573
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