Direct-drive manipulator for pen-based force display

Abstract

A pen-based direct-drive manipulator enables precision manipulation and force display of a control point within three degrees of freedom. The control point exhibits substantially no backlash, very low friction and very low inertia making it useful as a force display. The manipulator also has a very high force generation bandwidth allowing high frequency force components to be displayed. A parallel actuator structure controls motion over two degrees of freedom in a horizontal plane. The parallel structure is a redundant structure including three chains in parallel coupled at the control point. The redundant structure provides a uniform force capability throughout the manipulator workspace. A pair of rotational actuators rotate the parallel structure about an axis to approximate a linear motion along a third axis. The rotational actuators provide a third degree of freedom for the control point. Motion about the third axis is substantially decouple from motion about the horizontal plane.

Description

BACKGROUND OF THE INVENTIONThis invention relates to direct-drive manipulators and force feedback devices. More particularly this invention relates to a direct-drive manipulator having three degrees of freedom and suitable for use as a pen-based force display for a virtual reality or telerobotic environment.A manipulator can serve as an input device for controlling movement of a robot or other real or simulated device. A direct drive manipulator responds to operator manipulations using one or more actuators directly coupled to a load (on the output side) or an operator contact point (on the input side). This contrasts with an indirectly driven manipulator which responds to operator manipulations using one or more actuators indirectly coupled to the load or operator contact point through gears or other scaling devices.A pen-based manipulator is characterized by an elongated member having a contact point for applying operator input forces and displacements. The manipulator enables an ...

AI Technical Summary

Benefits of technology

According to one aspect of the invention, direct drive actuators are used for the manipulator. Direct drive actuators have force display advantages over indirect drive actuators. Indirect drive geared actuators have unacceptable backlash and friction characteristics. Also, indirect drive actuators typically have lower bandwidth capability. Direct drive actuators are implemented here in a configuration for a control point having no backlash, very low friction and very high force generation bandwidth.

According to another aspect of the invention the end-effector defines an open tool interface point as the control point. An operator holds his finger, a pen-like tool or other tool to the interface point and applies forces or displacements to manipulate the control point. By providing an open interface there is no friction or backlash introduces by a device that would hold the tool tip in place at the control point. Similarly the operator can apply or remove the tool from the control point with a natural feel. For example if the tool is a scalpel in a surgical virtual reality application, the trainee physician can manipulate the scalpel as during a real operation, then apply the scalpel to the control point to perform a cutting / surgical maneuver. The operator therefore achieves a more realistic making and breaking of contact.

According to another aspect of the invention, a pair of rotational actuators rotate the parallel structure about an axis to approximate a linear motion along a third axis, and provide a third degree of freedom for the control point.

One advantage of the manipulator of this invention is that embodiments have substantially no backlash, very low friction, very low inertia and a very high force generation bandwidth enabling a natural feel when implemented as a force display. Another advantage is that embodiments have a substantially uniform force capability throughout there workspace. These and other aspects and advantages of the invention will be better understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

Problems solved by technology

No matter how sophisticated a control algorithm, if the manipulator suffers from significant amounts of backlash, friction or inertia, then its use as a force display is compromised.

Indirect drive geared actuators have unacceptable backlash and friction characteristics.

Also, indirect drive actuators typically have lower bandwidth capability.

Images