Object-space teleoperation

Note: this work was done by our friend and colleague Paul Michelman, who passed away unexpectedly on June 30, 2000.

Contact: Peter Allen<allen@cs.columbia.edu>

Teleoperation is a principle means of controlling robot hands for industry and for prosthetics. The traditional way of teleoperating a robot hand has been using a Dataglove or exoskeleton master: there is a direct mapping from the human hand to the robot hand. Generally, the finger positions of the human master are translated to the robot and visual or force feedback are returned from the robot to the master. (See Speeter et al. [1992], Pao and Speeter [1989], Burdea et al. [1992]). There are several difficulties with this approach:

  1. Calibration: It is difficult to find a direct mapping from the human hand master to the robot. For example, Hong and Tan (Robotics &Automation, 1989) developed a complex three-step process each user must repeat.

  2. The capabilities of robot hands are different from those of human hands. For example, the human hand can translate objects along only a single axis while a hand such as the Utah-MIT hand has the ability to translate objects in three Cartesian directions. Using a Dataglove thus reduces the manipulatory capabilities of the robot hand.

  3. Autonomy: robot commands are displacements rather than functions. Without a high-level function, it is difficult to enhance a robot's autonomy. Furthermore, in situations in which there are long communication delays between the master and the robot (greater than 1 second), it is useful for the robot to perform certain functions autonomously (Bejczy and Kim [1990]).

  4. High degree-of-freedom force feedback is still experimental and expensive.

In this type of ``manual control,'' the interface between the robot and the user primarily transfers data and performs coordinate transformations. We propose to increase the autonomy of the robot hand by shifting the control space from the joint positions to the space of the grasped object (see Michelman and Allen [10]). Rather than translate the motions of a master's fingers directly to motions of the robot hand, a simple, low degree-of-freedom input device, such as a joystick, controls the motions of the manipulated object directly. The motions of the manipulated object normally involve a single degree of freedom; they are two-dimensional translations and rotations. The system in turn computes the required finger trajectories to achieve the motion. The use of a low degree-of-freedom input device is appealing because it alleviates the problems cited above related to difficulty of calibration, the high input and sensor bandwidths required for full telemanipulation. In addition, increasing the autonomy of the robot allows it to perform tasks such as maintaining grasp forces and resisting external disturbances automatically. Low DOF input devices can include voice recognition systems, trackballs, Spaceballs (The Spaceball is a multi-function input device that senses forces and moments applied to it. It also has an array of software programmable buttons that can be assigned functions during a task.), myoelectric signals, and other devices used in industry and rehabilitation. The basis of the object-centered teleoperation system is set of primitive manipulations described above.

Return to the Robotics Lab home page