Planar Haptic Interface Research Articles

Haptic Rendering and Manipulability of Cable-Based Planar Haptic Interface

Haptic Rendering and Manipulability of Cable-Based Planar Haptic Interface

Sophia-3: A Semiadaptive Cable-Driven Rehabilitation Device With a Tilting Working Plane

Sophia-3 (string-operated planar haptic interface for arm rehabilitation) is a planar cable-driven device with a tilting working plane. It represents the first application of the adaptive cable-driven design paradigm recently introduced by the authors, featuring a moving pulley-block that allows the robot to achieve excellent force capabilities, despite the low number of cables. This study presents the design, kinematics, and control of the device and results of experimental validation on healthy subjects.

Development and investigation of a semi-active polar planar haptic interface using the digital resistance map concept

The growing demand for haptic technologies in recent years has motivated novel approaches in developing haptic interfaces and control algorithms. Semi-active haptic interfaces, in general, have the advantage of addressing safety concerns which adversely affect their active counterparts. This paper presents the development of a planar semi-active haptic interface using magnetorheological (MR) dampers. The ability of MR dampers to produce controllable resistance forces is the key reason for their utilization in the proposed haptic interface. The proposed planar semi-active haptic interface consists of linear and rotary MR dampers. Each of the MR dampers is modeled experimentally using the Bouc–Wen model. A haptic rendering algorithm called the digital resistance map (DRM) is also developed to control MR dampers. DRM is a high-fidelity haptic rendering algorithm, and proved to be effective to create comprehensive force feedback for operators. MATLAB/Simulink® is used for implementing several DRM scenarios for generating haptic enabled virtual environments. The experimental results demonstrate the effectiveness of the proposed haptic interface and rendering algorithm.

Task performance evaluation of asymmetric semiautonomous teleoperation of mobile twin-arm robotic manipulators.

A series of human factors experiments involving maneuvering and grasping tasks are carried out to evaluate the effectiveness of a novel asymmetric semiautonomous teleoperation (AST) control design framework for teleoperation of mobile twin-arm robotic manipulators. Simplified configurations are examined first to explore control strategies for different aspects of such teleoperation tasks. These include teleoperation of a nonholonomic mobile base, telemanipulation of a dual-arm robot, and dual-arm/dual-operator teleoperation task scenarios. In two sets of experiments with a planar nonholonomic mobile base, teleoperation via a 3DOF planar haptic interface with position mapping and force reflection of the nonholonomic constraint decreases task-completion-time (TCT) and reduces unwanted collisions. In dual-arm and dual-operator teleoperation maneuverability experiments, the assignment of decoupled and nonconflicting control frames reduces TCT and unwanted contacts. The use of so-called "soft" constraints via passive semiautonomous control reduces TCT and unwanted block drops in telegrasping experiments with a twin-arm manipulator. A final comprehensive experiment encompassing elements of the simplified configurations demonstrates the effectiveness of AST control framework in dual-operator teleoperation of a twin-arm mobile manipulator.

Automated Characterization and Compensation for a Compliant Mechanism Haptic Device

Compliant mechanisms and voice coil motors can be used in haptic device designs to eliminate bearings and achieve smooth friction-free motion. The accompanying return-to-center behavior can be compensated using feedforward control if a suitable multidimensional stiffness model is available. In this paper we introduce a method for automatic self-characterization and compensation, and apply it to a planar haptic interface that features a five-bar compliant mechanism. We show how actuators and position sensors already native to typical impedance-type haptic devices can readily accommodate stiffness compensation. Although a portion of the motor torque is consumed in compensation, the device achieves smooth friction-free articulation with simple, low tolerance, and economic components. Empirical models built on self-characterization data are compared to standard empirical and analytical models. We produce a model by self-characterization that requires no inversion and is directly useable for compensation. Although our prototype compliant mechanism, which we fabricated in plastic using fused deposition modeling, exhibited hysteresis (which we did not compensate), the return-to-center behavior was reliably reduced by over 95% with feedforward compensation based on the self-characterized model.

Interactive Simulation of Needle Insertion Models

A novel interactive virtual needle insertion simulation is presented. The simulation models are based on measured planar tissue deformations and needle insertion forces. Since the force-displacement relationship is only of interest along the needle shaft, a condensation technique is shown to reduce the computational complexity of linear simulation models significantly. As the needle penetrates or is withdrawn from the tissue model, the boundary conditions that determine the tissue and needle motion change. Boundary condition and local material coordinate changes are facilitated by fast low-rank matrix updates. A large-strain elastic needle model is coupled to the tissue models to account for needle deflection and bending during simulated insertion. A haptic environment, based on these novel interactive simulation techniques, allows users to manipulate a three-degree-of-freedom virtual needle as it penetrates virtual tissue models, while experiencing steering torques and lateral needle forces through a planar haptic interface.

Manipulability of a planar wire driven haptic device

This paper presents a planar 4 wire driven 3-DOF mechanism. For a planar haptic interface, this device could provide planar forces and moment feedback to the human operator. The particular end-effector geometric configuration overcomes manipulability problems arising from other recent planar wire haptic interfaces [R.L. Williams II, Int. J. Virtual Reality 3 (3) (1998) 13]. Moreover, an explicit forward kinematic pose solution is obtained by introducing a modified wire configuration. Complete kinematic and manipulability analyses are presented.

Fast constrained global minimax optimization of robot parameters

A new global isotropy index (GII) is proposed to quantify the configuration independent isotropy of a robot's Jacobian or mass matrix. A new discrete global optimization algorithm is also proposed to optimize either the GII or some local measure without placing any conditions on the objective function. The algorithm is used to establish design guidelines and a globally optimal architecture for a planar haptic interface from both a kinematic and dynamic perspective and to choose the optimum geometry for a 6-DOF Stewart Platform. The algorithm demonstrates consistent effort reductons of up to six orders of magnitude over global searching with low sensitivity to initial conditions.