Philip Datseris

Basic considerations for robot calibration

The effect of kinematic model choice on robot calibration is examined. The literature on the subject is reviewed, and the various possible choices for kinematic modeling are examined. Problems of uniqueness and proportionality are discussed, and a closed-form method for extracting the parameters of a six-parameter model is shown.<<ETX>>

Improving Finite State Impedance Control of Active-Transfemoral Prosthesis Using Dempster-Shafer Based State Transition Rules

Finite state impedance (FSI) control is a widely used approach to control active-transfemoral prostheses (ATP). Current design of state transition rules depends on hard thresholding of intrinsic mechanical measurements, which cannot cope well with uncertainty related with intra- and inter-subject variations of these intrinsic recordings. In this study, we aimed to generate more robust FSI control of ATP against these variations by using Dempster-Shafer theory (DST)-based transition rules. The FSI control with DST-based rules was implemented on an instrumented ATP, evaluated on five able-bodied subjects and one patient with a unilateral transfemoral amputation. Then the DSP based transition rules were compared to the control with hard threshold (HT)-based transition rules. The results showed that when compared to the hard thresholding approach, the DST yielded enhanced accuracy in state transition timing and reduced control errors when intra- and inter-subject variations were presented. Additionally, the parameters of DST-based rules were uniform for all the subjects tested, allowing for easy and efficient transition rule design and calibration. The outcome of this study can lead to further improvement of robust, practical, and self-contained ATP design, which in turn will advance the motor function of patients with lower limb amputations.

A Prototype for Smart Prosthetic Legs-Analysis and Mechanical Design

In this paper, we designed a prototype of powered above-knee prosthesis. Compared with other prototypes available in the literature, our designed prosthetic leg employs a redundant actuator concept to overcome the challenge faced by the single-motor transmission systems. The redundant actuator also enables the prosthesis to be partially functional when the prosthesis loses power. Finally, in order to provide optimal control parameters for designed above-knee prosthesis to perform a smooth level-ground walking task, an inverse dynamic model based on Kane’s method is constructed.

A flexible automated foam cutting system

Direct cutting of foam has the advantage of greater flexibility and reduced lead time over molding. This paper discusses the design and development of a flexible automated system for foam cutting that utilizes hot-wire cutters. The cutters are moved through the use of a five-axis gantry-type robot system equipped with a tool turret. A method for modeling the cut geometry, based on representing the three-dimensional cut shape as a combination of basic geometrical block shapes, is presented. This method gives the system flexibility to handle different workpiece geometries. A technique for generating the required cutting paths from the modeled geometry is also shown. The developed methodology was applied for the cutting of automotive seat cushions. The results show that the automated system significantly reduces the cutting time and produces cuts of improved quality.

A manufacturing system for automated production of polystyrene molds

A compact automated system cuts complicated contours on prefabricated polystyrene blocks which are used as molds to cast Cerrobend, which is used as a shield in radiation therapy. The authors describe the development of the prototype, including details for machine configuration, motion planning and cutting experiments.

Development of a position and force sensor for robotic applications

A position/force sensor is developed to determine the position, distribution and magnitude of the load applied by an object on the sensor. For robotic applications, the sensor can be attached to grippers to aid in determining the relative pose between object and gripper, as well as in determining three forces and three moments. The sensor is designed to function as a tactile sensor and a robot wrist force sensor. Theory of plates is employed for sensor design. Strains are measured from direct contact to provide more precise position and force information. Control algorithns for robot hand motion during assembly are developed from the study and understanding of parts mating.

A workspace optimization approach to manipulator linkage design

The manipulator design problem is discussed. A method is presented for the calculation of workspace volume of generalized manipulators which include both revolute and prismatic joints. For a fixed length of generalized manipulator including both types of joints, optimization of workspace volume leads to specific manipulator configurations. Industrial robot manipulators resemble the optimized configurations, and so do animal limbs when the first three joints are revolute. Two of the optimized manipulators, however, do not have parallels in industry.

Pose-seeking algorithms for the control of dexterous robot hands

In applications of manipulating, or dexterous robot hands, it is necessary to use sensors and suitable algorithms to determine the pose of the workpiece when it is acquired by the hand so that it can be brought to the desired final pose. The feedback obtained from common hand sensors such as tactile arrays and optical through-beam pairs is intermittent, and therefore control algorithms are needed to manipulate the workpiece so as to activate these sensors to obtain pose information with the least amount of manipulation. A hand that manipulates cylindrical-type workpieces in five degrees of freedom is used as an illustration. A pose-seeking algorithm using the hands through-beam sensors is presented, and theoretical foundations are laid for extending the work to include other types of workpieces.

Orientation and stacking of parts based on internal features

Orientation and stacking of parts has been mostly based on their external features. There are a number of parts which need to be oriented and stacked based on internal features, either because internal features are of primary importance or because of lack of appropriate external features. Issues concerning the orientation and stacking of parts based on their internal features are investigated and two-dimensional axi-symmetrical parts have been classified into groups based on both internal and external features. Fundamental methodologies have been developed for orienting and stacking of parts based on internal features and experimental verification has been performed for many cases. Results indicate that parts can be oriented efficiently and at high speeds. In addition, it can be concluded from these experiments that in many cases, the widely accepted rule that orientational position of parts should be preserved does not necessarily hold.