Haptic Guides: Providing Usable Force Feedback Information in Time Critical Tasks - Ben Forsyth Table of Contents: - Abstract - Problem - Solutions - Experimental Setup - References

## Abstract

Cars of the future will know much more about their surrounding environment. We are looking for ways to use this information to make driving safer and easier. We are investigating a family of control algorithms that use this information to provide driving suggestions via force feedback through the steering wheel. We have developed some prototype control methods that attempt to take into account how users reflexively react to guiding forces in time critical situations.

## Problem

What is an effective way to effectively provide lateral guidance using haptics?
Common problems making this difficult:

## Overshoot

Overshoot typically happens at sharp corners and causes large reaction forces that lead to another overshoot and so on.

## Oscillation

Naive control methods can create forces that throw a user back and forth between the walls of a channel.

## Problems with the User's Understanding and Reactions to Forces:

There are a number of problems involved in making haptic path guidance usable and informative:
• The user doesn't understand what the forces mean
• The user is startled by the forces and fights them reflexively
• The user understand what the forces mean but wants to ignore them and do something else
• The user needs to understand what the forces mean very quickly

## Spring and Damper

The user's location is tied to the path by a virtual spring and damper. This is the easiest path guidance control method to implement but leads to the overshoot problem in some circumstances.

This is a method that has been used for autonomous control and we are adapting it to haptics [1]. The current velocity of the control point is used to predict where we will be in the future. The point on the guidance path nearest to the predicted location is used as a target to steer the user towards.

## Potential Field

The user feels a force pushing them away from the sides of the channel towards the middle. This is an easy method to implement for channel guidance but can lead to the oscillation problem.

## Wall Offset

The current velocity of the control point is used to predict the location of the user sometime in the future. If this predicted position is outside of the channel, the user is steered towards a location inside the channel.

## 'Feelers'

When a 'feeler' comes in contact with a wall, the user is steered away from the wall. Similar to the Potential Field method but it only pushes on you when you are moving towards a side of the channel, which should eliminate oscillations.

## Experimental Setup

We will implement the control methods on haptic device called the PHANToM by SensAble Technologies. This gives us more control than a standard force feedback steering wheel. We will test and optimize the effectiveness of the control methods using iterative user testing.

## References

[1] Reynolds, Craig. Steering behaviors for Autonomous Characters, Game Developers Conference 99.

Last Updated On:
September 25, 2003 4:07 PM