Design and Validation of a Variable Stiffness Three Degree of Freedom Planar Robot Arm

The need exists for robotic manipulators that can interact with an environment having uncertain kinematic constraints. A robot has been designed and built for proof of concept of a passive variable compliance control strategy that can vary joint stiffness to achieve higher performance dexterous manipulation. This novel planar robot incorporating variable stiffness actuators and common industrial controls allows the robot to comply with its environment when needed but also have high stiffness for precise motion control in free space. To perform both functions well, a high stiffness ratio (max/min stiffness) is required. A stiffness ratio up to 492 was achieved. The robot performance was evaluated with the task of turning a crank to lift a weight despite nominal positioning inaccuracy. The novel variable stiffness robot was able to complete the task faster and with lower constraint forces than a traditional force-controlled stiff robot. The time to complete the task using passive variable stiffness control was twenty-nine times faster with constraint forces less than one fifth those achieved using traditional active compliance control

A review on humanoid robotics in healthcare

Humanoid robots have evolved over the years and today it is in many different areas of applications, from homecare to social care and healthcare robotics. This paper deals with a brief overview of the current and potential applications of humanoid robotics in healthcare settings. We present a comprehensive contextualization of humanoid robots in healthcare by identifying and characterizing active research activities on humanoid robot that can work interactively and effectively with humans so as to fill some identified gaps in current healthcare deficiency

Design and test of a Displacement Workspace Mapping Station for articular joints

In 2003, 267,000 Americans received total knee replacements prohibiting high impact athletics for the remainder of a patient’s life. A better understanding of the movement and constraint of the knee is necessary to provide more realistic motion of or possibly eliminate the need for joint prosthetics. Fixed Orientation Displacement Workspaces (FODW) can be applied to study the relationship of the passive constraint system and six (6) degree of freedom (DOF) movement of the human knee. A FODW consists of the volume of possible positions the tibia/fibula can occupy relative to a fixed femur without changing the relative orientation of the bones. Theoretical models of the FODW provided a promising snapshot of knee kinematics. A Displacement Workspace Test Station (DWTS) for mapping FODWs was built. An in vitro articular joint completes the loop between a strain gauge-based six (6) axis load cell and a 6 DOF manipulandum mounted to a fixed reference frame. The joint is hand manipulated while a C++ program, Armtalk, operates applications that sample and filter both manipulandum position/orientation and load cell output signals at over 500Hz. Armtalk automatically stores raw data points at 2 Hz or upon a user foot-pedal signal. Forces and moments acting at the joint and its angular orientation are added to each raw data point by algorithms in a spreadsheet. The algorithms select points that represent a particular FODW according to a user specified range of acceptable joint forces and moments and bone orientations. The Cartesian coordinates of individual FODW data points are input into a NURBS-based CAD program for visualization. The DWTS has a 0.2286 mm positional accuracy, a 200 N capacity, and a 0.075 mm/kN compliance. A 2 DOF test checked the Armtalk application and calculated the DWTS angular accuracy to be 0.008°. To calibrate the load cell, moment and force scaling factors of 0.00922 in lb/unit and 0.00554 lb/unit were calculated, respectively. The spreadsheet algorithms successfully reduced data in a 6 DOF test. The CAD program modeled workspaces from 2 and 6 DOF tests with a 1.3 % volumetric accuracy. The apparatus is ready to map FODW of articular joints

Robotics for nuclear waste handling

This research focuses on the development of the control system of a dual arm industrial robot. A controller for the position control of unconstrained robot arm is also presented. System architecture, hardware configuration and software development are discussed in detail; The experimental set-up consists Remotec\u27s RM-10A dual arm manipulator. Each arm has six separate motorized motions with position sensors. The manipulator is controlled by a Texas Istruments\u27 TMS320C40 parallel Digital Signal Processors installed on the QPC/C40B Board. The PID control software which is embedded on the Digital Signal Processor is developed using C language. A Graphical User Interface is also developed using Microsoft Visual C{dollar}\sp{++}{dollar} to facilitate easy operation of the robot

Autonomous Visual Servo Robotic Capture of Non-cooperative Target

This doctoral research develops and validates experimentally a vision-based control scheme for the autonomous capture of a non-cooperative target by robotic manipulators for active space debris removal and on-orbit servicing. It is focused on the final capture stage by robotic manipulators after the orbital rendezvous and proximity maneuver being completed. Two challenges have been identified and investigated in this stage: the dynamic estimation of the non-cooperative target and the autonomous visual servo robotic control. First, an integrated algorithm of photogrammetry and extended Kalman filter is proposed for the dynamic estimation of the non-cooperative target because it is unknown in advance. To improve the stability and precision of the algorithm, the extended Kalman filter is enhanced by dynamically correcting the distribution of the process noise of the filter. Second, the concept of incremental kinematic control is proposed to avoid the multiple solutions in solving the inverse kinematics of robotic manipulators. The proposed target motion estimation and visual servo control algorithms are validated experimentally by a custom built visual servo manipulator-target system. Electronic hardware for the robotic manipulator and computer software for the visual servo are custom designed and developed. The experimental results demonstrate the effectiveness and advantages of the proposed vision-based robotic control for the autonomous capture of a non-cooperative target. Furthermore, a preliminary study is conducted for future extension of the robotic control with consideration of flexible joints

New Mechatronic Systems for the Diagnosis and Treatment of Cancer

Both two dimensional (2D) and three dimensional (3D) imaging modalities are useful tools for viewing the internal anatomy. Three dimensional imaging techniques are required for accurate targeting of needles. This improves the efficiency and control over the intervention as the high temporal resolution of medical images can be used to validate the location of needle and target in real time. Relying on imaging alone, however, means the intervention is still operator dependent because of the difficulty of controlling the location of the needle within the image. The objective of this thesis is to improve the accuracy and repeatability of needle-based interventions over conventional techniques: both manual and automated techniques. This includes increasing the accuracy and repeatability of these procedures in order to minimize the invasiveness of the procedure. In this thesis, I propose that by combining the remote center of motion concept using spherical linkage components into a passive or semi-automated device, the physician will have a useful tracking and guidance system at their disposal in a package, which is less threatening than a robot to both the patient and physician. This design concept offers both the manipulative transparency of a freehand system, and tremor reduction through scaling currently offered in automated systems. In addressing each objective of this thesis, a number of novel mechanical designs incorporating an remote center of motion architecture with varying degrees of freedom have been presented. Each of these designs can be deployed in a variety of imaging modalities and clinical applications, ranging from preclinical to human interventions, with an accuracy of control in the millimeter to sub-millimeter range

Optimization of 3-DOF Parallel Motion Devices for Low-Cost Vehicle Simulators

Motion generation systems are becoming increasingly important in certain Virtual Reality (VR) applications, such as vehicle simulators. This paper deals with the analysis of the Inverse Kinematics (IK) and the reachable workspace of a three-degrees-of-freedom (3-DOF) parallel manipulator, proposing different transformations and optimizations in order to simplify its use with Motion Cueing Algorithms (MCA) for self-motion generation in VR simulators. The proposed analysis and improvements are performed on a 3-DOF heave-pitch-roll manipulator with rotational motors, commonly used for low-cost motion-based commercial simulators. The analysis has been empirically validated against a real 3-DOF parallel manipulator in our labs using an optical tracking system. The described approach can be applied to any kind of 3-DOF parallel manipulator, or even to 6-DOF parallel manipulators. Moreover, the analysis includes objective measures (safe zones) on the workspace volume that can provide a simple but efficient way of comparing the kinematic capabilities of different kinds of motion platforms for this particular application