Automated Characterization and Compensation for a Compliant Mechanism Haptic Device (original) (raw)

Design and evaluation of a high-performance haptic interface

Robotica, 1996

SUMMARYA haptic interface is a computer-controlled mechanism designed to detect motion of a human operator without impeding that motion, and to feed back forces from a teleoperated robot or virtual environment. Design of such a device is not trivial, because of the many conflicting constraints the designer must face.As part of our research into haptics, we have developed a prototype planar mechanism. It has low apparent mass and damping, high structural stiffness, high force bandwidth, high force dynamic range, and an absence of mechanical singularities within its workspace. We present an analysis of the human-operator and mechanical constraints that apply to any such device, and propose methods for the evaluation of haptic interfaces. Our evaluation criteria are derived from the original task analysis, and are a first step towards a replicable methodology for comparing the performance of different devices.

A stiffness modeling methodology for simulation-driven design of haptic devices

Engineering with Computers, 2012

Efficient development and engineering of high performing interactive devices, such as haptic robots for surgical training benefits from model-based and simulation-driven design. The complexity of the design space and the multi-domain and multi-physics character of the behavior of such a product ask for a systematic methodology for creating and validating compact and computationally efficient simulation models to be used in the design process. Modeling the quasi-static stiffness is an important first step before optimizing the mechanical structure, engineering the control system, and performing hardware in the loop tests. The stiffness depends not only on the stiffness of the links, but also on the contact stiffness in each joint. A fine-granular Finite element method (FEM) model, which is the most straightforward approach, cannot, due to the model size and simulation complexity, efficiently be used to address such tasks. In this work, a new methodology for creating an analytical and compact model of the quasi-static stiffness of a haptic device is proposed, which considers the stiffness of actuation systems, flexible links and passive joints. For the modeling of passive joints, a hertzian contact model is introduced for both spherical and universal joints, and a simply supported beam model for universal joints. The validation process is presented as a systematic guideline to evaluate the stiffness parameters both using parametric FEM modeling and physical experiments. Preloading has been used to consider the clearances and possible assembling errors during manufacturing. A modified JP Merlet kinematic structure is used to exemplify the modeling and validation methodology.

The ultimate haptic device: First step

World Haptics 2009 - Third Joint EuroHaptics conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, 2009

We describe a single-axis haptic interface which is based on a dualstage actuator technique and which is aimed at achieving perfect transparency to a human user. The paper shows how all parasitic forces arising from inertia and friction can be brought below human detection thresholds, yet, the system is able to output significant torque. It has a stage with a large motor coupled to a distal stage with a smaller motor via a viscous coupler based on the principle of eddy current induction. The paper also describes its control principle and preliminary results.

A model-based and simulation-driven methodology for design of haptic devices

Mechatronics, 2014

High precision and reliable haptic devices are highly complex products. The complexity that has to be carefully treated in the design process is largely due to the multi-criteria and conflicting character of the functional and performance requirements. These requirements include high stiffness, large workspace, high manipulability, small inertia, low friction, high transparency, as well as cost constraints. The requirements are a basis for creating and assessing design concepts. Concept evaluation relies to a large extent on a systematic usage of kinematic, dynamic, stiffness, friction, and control models. The design process can benefit from a model-based and simulation-driven approach, where one starts from an abstract top-level model that is extended via stepwise refinements and design space exploration into a detailed and integrated systems model that can be physically realized. Such an approach is presented, put in context of the V-model, and evaluated through a test case where a haptic device, based on a Stewart platform, is designed and realized. It can be concluded, based on simulation and experimental results that the performance of this deterministically optimized haptic device satisfies the stated user requirements. Experiences from this case indicate that the methodology is capable of supporting effective and efficient development of high performing haptic devices. However, more test cases are needed to further validate the presented methodology.

ROBOTIC IMPEDANCE CONSTRAINTS FOR HAPTIC FEEDBACK

In the approach presented in this research, a six DOF industrial manipulator is used as the master device to provide haptic feedback to the operator. In order develop effective constraints between the motion of the slave and master, a virtual manipulator concept is developed that couples the actual robotic kinematics with the constraints of the simulated slave manipulator. The position and velocity errors between the actual and virtual mechanisms are used to develop an optimal impedance controller that constrains the motion of the master in all directions that are orthogonal to the allowable motions of the slave. This approach allows the use of a conventional industrial manipulator as an effective haptic display device.

Friction Modeling and Compensation for Haptic Interfaces

Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, 2005

Friction cancellation and high gain force feedback are studied for their relative beneìts in mitigating the effects of friction in haptic interfaces. Although either technique alone is capable of signiìcant improvements, we ìnd that a combination of approximate cancellation coupled with variable-gain low-bandwidth force feedback provides ex- cellent friction reduction and is more robust. This improves the feel of the

An approach to stiffness analysis methodology for haptic devices

In this work a new methodology is proposed to model the static stiffness of a haptic device. This methodology can be used for other parallel, serial and hybrid manipulators. The stiffness model considers the stiffness of; actuation system; flexible links and passive joints. For the modeling of the passive joints a Hertzian contact model is introduced for both spherical and universal joints and a simply supported beam model for universal joints. For validation of the stiffness model a modified JP Merlet kinematic structure has been used as a test case. A parametric Ansys FEM model was developed for this test case and used to validate the resulting stiffness model. The findings in this paper can provide an additional index to use for multi-objective structural optimization to find an optimum compromise between a lightweight design and the stiffness performance for high precision motion within a larger workspace.