Position Degrees Of Freedom Research Articles

Kinematic Synthesis of Manipulators Using a Distributed Optimization Method

In this paper, the rigid body guidance problem of general 6 degree of freedom manipulators is studied. A new method, called Distributed Optimization Method (DOM), is used to determine the dimensional parameters of general manipulators that are able to reach a finite number of given six degree of freedom position and orientation tasks. It is shown that the global multi-variable optimization problem of kinematic synthesis can be solved as a sequence of local, one variable, optimization problems. The new method allows the possibility to include additional criteria in the manipulator kinematic synthesis such as joint limits, range of dimensional parameters, obstacles avoidance, isotropy and number of configurations to reach a specific end-effector task. Two examples are given to illustrate the validity of the method.

Spatially continuous six degree of freedom position and orientation sensor

This paper describes SHAPE TAPE™, a thin array of fiber optic curvature sensors laminated on a ribbon substrate, arranged to sense bend and twist. The resulting signals are used to build a three dimensional computer model containing six degree of freedom position and orientation information for any location along the ribbon. The tape can be used to derive dynamic or static shape information from objects to which it is attached or scanned over. This is particularly useful where attachment is only partial, since shape tape “knows where it is” relative to a starting location. Measurements can be performed where cameras cannot see, without the use of magnetic fields. Applications include simulation, film animation, computer aided design, robotics, biomechanics, and crash testing.

Six Degrees of Freedom Position and Posture Control for a Quadruped Robot

This paper describes a position and posture control method for a quadruped robot and its experimental results. One of the advantages of legged robots is the capability to change the body position and posture without changing the foot points. Considering practical applications for legged robots, it is important to control the position and posture of the robot body. In this method, three translational velocity and three angular velocity commands are provided simultaneously.

A “3-2-1” kinematic configuration of a Stewart platform and its application to six degree of freedom pose measurements

This paper outlines a simple yet accurate approach to measuring the six degree of freedom position and orientation of a robot end-effector. The mechanism, which will be far less costly than currently available devices, can be used to make both static and dynamic measurements for robot calibration as well as real-time endpoint control. The kinematics of the approach stem from a configuration of the Stewart platform. A “3-2-1” kinematic configuration is proposed which results in a closed-form forward kinematic solution for the Stewart platform. The closed-form algorithm can be computed about 100 times faster than conventional iterative algorithms. A prototype system using six string encoders was built and tested. Issues on error compensation were also studied. The presented approach should be useful for a broad range of applications other than robot metrology where convenient, low-cost, six degree of freedom static and/or dynamic pose measurements are required or preffered.

Using a Maximum Error Statistic to Evaluate Measurement Errors in 3D Position and Orientation Tracking Systems

One approach to tracking anatomical and robot joint motion consists of tracking the XYZ locations of multiple point targets that are attached to each of the moving segments and then computing the three translations and three orientation angles between adjoining segments. The complexity of such systems requires that we introduce a new conservative maximum error statistic to be used for evaluating the accuracy of 3D motion tracking systems. This paper addresses the various phenomena that contribute to measurement error when computing six degrees of freedom associated with the relative motion between the adjacent segments. The characteristics of these errors, common to many 3D motion tracking systems, were first determined by experimentation using one such system (MnSCAN). These and additional artifacts were then modeled in order to quantitatively evaluate their effects using the maximum error statistic. Based on these computer experiments, several relationships were identified that predict how each of these phenomena influences the predicted measurement of relative motion between bodies. These suggest where design emphasis should be placed in order to minimize the error in tracking the six degrees of freedom. The methodology and the conclusions based on these results can be applied to designing most six degree of freedom position and motion measurement systems.

The Characterization of a Grain Boundary by Transmission Electron Microscopy

Read has shown that an arbitrary grain boundary has five degrees of freedom associated with it. Three degrees of freedom are necessary to describe the orientation of one grain with respect to the other, while the remaining two degrees of freedom position the boundary plane between the adjacent grains.Figure 1(a) depicts a general twin boundary-grain boundary intersection. The degrees of freedom for the grain boundary are represented by (HKL)1, (HKL)2, Θ, θGB, ø. Two degrees of freedom are contained in the surface orientations of the grains.