A continuously variable transmission system designed for human-robot interfaces

Continuously Variable Transmission (CVT) systems are being used for many applications such as automotive transmissions, robotics, aerospace. In an ideal condition, these systems have the potential to provide continuously varying power transmission within a predefined limit. This transmission is accomplished with the help of friction, belt or gear systems. CVT can find application in a human-robot interface if design criteria such as backdrivability, independent output position and impedance variation, shock absorbing and low mass and inertia can be satisfied. Even if there are various CVT designs in the literature for human-robot interfaces, the primary limitation of the two-cone drive CVT designs is that the output torque and the output position cannot be altered independently. The reason for this problem is that the friction wheel, which is designed to transmit the torque from the input cone to the output cone, gives rise to remarkable longitudinal friction force along the linear way. In order to overcome this problem, a sphere is used in this work for the CVT design as the transmission element. In addition, it is stated in the literature that common CVT drive systems do not have the capability to be used in cyclic bidirectional motion. In the presented CVT design, a second sphere is added to the system with two springs from the lower part of the cones for pre-tension in order to solve the bidirectional transmission problem. In this paper, the working principle and conceptual design details of the novel two-cone CVT drive are presented. Experimental results showed that the novel CVT has the capacity to transmit bidirectional power with some accuracy.The Scientific and Technological Research Council of Turkey (grant number 117M405

A survey on uninhabited underwater vehicles (UUV)

ASME Early Career Technical Conference, ASME ECTC, October 2-3, 2009, Tuscaloosa, Alabama, USAThis work presents the initiation of our underwater robotics research which will be focused on underwater vehicle-manipulator systems. Our aim is to build an underwater vehicle with a robotic manipulator which has a robust system and also can compensate itself under the influence of the hydrodynamic effects. In this paper, overview of the existing underwater vehicle systems, thruster designs, their dynamic models and control architectures are given. The purpose and results of the existing methods in underwater robotics are investigated

On the formulation of parallel position/force control schemes for industrial manipulators

In this paper, three commonly-used position/force control schemes namely Impedance, Admittance and Hybrid Position/Force control are investigated for use in industrial manipulators. In order to eliminate the instability problem that may occur in the customary versions of these schemes for large position errors, a modification is proposed, which is based on determining the joint-space position errors using inverse kinematic solutions rather than using the inverse Jacobian matrix. The feasibility of this modification relies on the fact that almost all of the industrial manipulators have easily obtainable inverse kinematic solutions. The simulation results showing the performance of the modified control schemes are also presented as applied on a Puma 560 manipulator

A study on selecting the method of constructing the information to be exchanged in unlimited-workspace bilateral teleoperation

In this paper, a study on selecting the mapping method for information exchange in unlimitedworkspace teleoperation is presented. In spite the fact that in most of the bilateral teleoperation systems, the master system sends motion demands and receives interaction force from the slave system, the information to be exchanged through the communication line between master and slave is selected to be force in both directions in this study. This approach is expected to ease the navigation of the user when a limited-workspace master system is used to control an unlimited-workspace slave system. As the unlimited-workspace slave system, a virtual flying scalpel is used and human skin is modeled to represent the environment around the slave system. Two methods of constructing force information, or in other words, information mapping between the two systems, are developed and evaluated via user studies. However, one of them comes out to provide acceptable results in the selected unlimited-workspace teleoperation task. Experimental results for the method that provides acceptable results are presented

A macro-micro mechanism design for laser cutting process

This paper is organized to provide the novel approaches during the design of a machine to shorten the laser cutting process. Macro-micro manipulation concept is employed for the design of this machine both in the mechanical design and in devising the trajectory planning algorithm. Micro-mechanism design along with its calibration process are also explained since they involve novel approaches in this application domain. Trajectory planning algorithms, which are developed in this work, are discussed based on their applicability to CNC system architecture. Finally, experimental results based on a benchmark workpiece are given and the system design is discussed with respect to these results.Republic of Turkey Ministry of Science, Industry and Technology and Coşkunöz Metal Form Inc. (Project code: 01668.STZ.2012-2

Kinematic design of a non-parasitic 2R1T parallel mechanism with remote center of motion to be used in minimally invasive surgery applications

In minimally invasive surgery applications, the use of robotic manipulators is becoming more and more common to enhance the precision of the operations and post-operative processes. Such operations are often performed through an incision port (a pivot point) on the patient's body. Since the end-effector (the handled surgical tool) move about the pivot point, the manipulator has to move about a remote center of motion. In this study, a 3-degrees-of-freedom parallel mechanism with 2R1T (R: rotation, T: translation) remote center of motion capability is presented for minimally invasive surgery applications. First, its kinematic structure is introduced. Then, its kinematic analysis is carried out by using a simplified kinematic model which consists of three intersecting planes. Then the dimensional design is done for the desired workspace and a simulation test is carried out to verify the kinematic formulations. Finally, the prototype of the final design is presented.Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK

Integration of the hybrid-structure haptic interface: HIPHAD v1.0

Design, manufacturing, integration and initial test results of the 6-DoF haptic interface, HIPHAD v1.0, are presented in this paper. The hybrid haptic robot mechanism is composed of a 3-DoF parallel platform manipulator, R-Cube, for translational motions and a 3-DoF serial wrist mechanism for monitoring the rotational motions of the handle. The device is capable of displaying point-type of contact since only the R-Cube mechanism is actuated. The dimensions and the orientation of the R-Cube mechanism are reconfigured to comply with the requirements of the haptic system design criteria. The system has several advantages such as relatively trivial kinematical analysis, compactness and high stiffness. The integration of the system along with its mechanism, data acquisition card (DAQ), motor drivers, motors, position sensors, and computer control interface are outlined.Marie Curie International Reintegration Grant within the 7th European Community Framework Programm

A comparative study on application of decomposition method in function generation synthesis of over-constrained mechanisms

Double-spherical six-bar linkage is one of the Bennett over-constrained 6R linkages. Kinematic synthesis of such linkages can be tedious and impossible to solve for analytically. In order to cope with higher number of unknowns in these types of linkages, decomposition method is a valuable tool. This paper focuses on the function generation synthesis of double-spherical six-bar linkage. Two procedures for applying decomposition method are explained. Two numerical studies are conducted for both procedures to evaluate the performance of each procedure

Function generation synthesis of planar 5R mechanism

This paper deals with the function generation problem for a planar five-bar mechanism. The inputs to the mechanism are selected as one of the fixed joints and the mid-joint, whereas the remaining fixed joint represents the output. Synthesis problem of the five-bar mechanism is analytically formulated and an objective function is expressed in polynomial form. Function generation synthesis is performed with equal spacing and Chebyshev approximation method. The four unknown construction parameters and the error are evaluated by means of five design points and the coefficients of the objective function are determined by numerical iteration using four stationary and one moving design point. Stationary points are placed at the boundaries of the motion and the moving point is re-selected at each iteration as the point corresponding to the extremum error. Iterations are repeated until the values are stabilized. The stabilization usually occurs at the third iteration. By this method, the maximum error values are approximately equated, hence the total error is bounded at certain limits. Finally the construction parameters of the mechanism are determined

Applying model mediation method to a mobile robot bilateral teleoperation system experiencing time delays in communication

Teleoperation systems consist of two subsystems namely, the master and the slave. Master is used by the human operator to send commands to the slave to achieve a task. In bilateral teleoperation, the interaction forces acquired from the slave sub-system is sent to the master to increase the level of tele-presence. In this kind of a setting, data has to be transferred through a communication line in which package losses and time delays occur. Such deficiencies in the communication line results in stability problems in the system. In this paper, HIPHAD desktop haptic device as the master sub-system and an omni-directional mobile robot as the slave subsystem is used to develop an unlimited workspace teleoperation system. The system’s stability and tracking performance under a constant time delay is measured for direct teleoperation and when model mediation method is applied to ensure stability. The results of the tests are given and the conclusions are derived.The Scientific and Technological Research Council of Turke