LIMS Projects - Scooter

Scooter and Modifications

Students:
Eric Faulring
Brent Gillespie
Aaron Mills
Boy Eng Seng
Wit Wannasuphoprasit

Professors:
Ed Colgate
Michael Peshkin

Quick Links:
Learning Cobot | Pallet Jack | Initial Build

Modification 2 -- Learning Cobot:

Students:

Boy Eng Seng

Thumbnails:

The scooter cobot exhibits two types of motion: free mode and constrained mode. In free mode, it behaves like a chair with casters (not exactly) and in constrained mode, it behaves like a train moving along a virtual "railway". The only difference is that the scooter can rotate as it moves along the "railway". Moreover, this virtual "railway" or the ideal path can be defined by the operator in software. When the scooter cobot is in constrained mode, it benefits its human operator by reducing 3 degrees of freedom (position and orientation) to just one degree of freedom (position along the ideal path) which is easier to control. As a result, the scooter cobot functions like a motion guide which reduces the need to manipulate by its operator. This benefit has interested several companies which includes General Motors and Toyota, to use cobots in their factories so as to reduce work-related injuries due to excessive manipulation of heavy loads by their workers.

Scooter cobot moving in constrained mode

The goal of this research is to develop an easy and efficient method to define a good ideal path. A path optimal to one person may not be optimal to another due to different personal preferences and physiques. In order to take these factors into account, a teach pendant will be used to define the ideal path. The key idea is to have the operator move the scooter along the intended ideal path and the traced path will be recorded and used as the ideal path for subsequent motions. The scooter hence learns from its operator what is his ideal path.

It is also important for the operator to be able to avoid obstacles and/or danger found in his work environment. The operator must be able to move off the ideal path when in need. The solution is an elastic path comfortable to the operator. The elastic path enables the operator to move the scooter away from it and achieves a level of shared control between the human and the scooter.
When the teach pendant and the elastic path work hand-in-hand, the scooter cobot will be able to record path segments deviated from the ideal path. These path segments can then be used to modify the existing ideal path. This strategy, called collaborative learning, enables the operator to modify the ideal path as his work environment changes. He may also use this strategy to optimise the ideal path over time when he becomes more familiar with the scooter cobot.
This project is done in collaboration with the National University of Singapore, Control and Mechatronics Laboratory (COME).

A typical path traced by a human subject. Bold lines and circles represent the applied force and torque respectively. Red bold lines are obstacles.

More Info:
The Learning Cobot (National University of Singapore)
National University of Singapore Control and Mechatronics Laboratory (COME)

Modification 1 - Pallet Jack:

Students:

Eric Faulring

Humans interact with many types of human propelled wheeled vehicles such as pallet jacks in warehousing and manufacturing environments. These systems typically do not have more than one steerable wheel (mechanically linked to the handle) and have no automated docking or path tracking modes. The addition of a handle to Scooter is for the purpose of investigating what intelligent three wheel steering modes and automated docking and path tracking modes might be advantageous. Also of interest is the transition between a "free" mode where the user is steering the device and a "constrained" mode where Scooter is tracking a path. This transition must occur along a path in three dimensions. Some research into extending planar clothoid curves to three dimensions has been undertaken.

A paper presented at IMECE 2002 is available here.
Eric Faulring's Masters Thesis is available here.

Initial Build:

Students:

Brent Gillespie, Aaron Mills, Wit Wannasuphoprasit

Thumbnails:

AVI clip (25.5MB) of Scooter at GM:

Papers:

Aaron L. Mills

Title
An Analysis of Position and Velocity Sensor Systems for a 3-Degree-of-Freedom Planar Collaborative Robot

Abstract
This thesis describes several methods for determining the position and velocity of a three degree-of-freedom planar collaborative robot (cobot). A cobot is a type of robotic device intended to assist a human operator through direct interaction. A planar cobot is designed to roll on a flat surface. Planar cobots require precise and continuous knowledge of their position and velocity to interact smoothly and intuitively with the operator. Based on these performance requirements, several position and velocity sensor systems have been implemented and compared. The sensor systems described in this thesis are either based on an odometry or a vision configuration and use one of several numerical methods to estimate the position and velocity. Experimental and theoretical analyses of these systems are used to evaluate the relationship between the sensor system and cobot performance.

Source: Master's thesis, Department of Mechanical Engineering, Northwestern University, March, 1998

Witaya Wannasuphoprasit, R. Brent Gillespie, J. Edward Colgate, and Michael A. Peshkin

Title
Cobot Control

Abstract
Cobots are a class of mechanically passive robotic devices, intended for direct physical collaboration with a human operator. The operator supplies all motive power while the cobot enforces software-defined guiding surfaces, or constraints. Cobots are intrinsically passive, safe devices. This is because, rather than employ powered actuators to produce constraint forces, cobots use "steerable" nonholonomic joints. Constraint forces are mechanical in origin, yet software defined.

The simplest possible cobot is a unicycle which is steered by a servo system acting under computer control, but which is moved by a human operator. The unicycle cobot requires essentially no consideration of kinematics. Two fundamental control modes of the unicycle cobot, "virtual caster" and "constraint tracking", are reviewed.

More complicated cobots, such as the three-wheeled "Scooter", require a set of kinematic transformations relating configuration space to joint space. These transformations play a role in cobot control like that of the jacobian in robot control.

Source: edings of the 1997 IEEE International Conference on Robotics and Automation, Albuquerque, NM, pp. 3571-3577

Last updated BPD 8/29/05.