Proxim RangeLAN2 7920 Uživatelský manuál stáhnout pdf (Strana 46)

•

FJk

− > 0 (the system is over-damped)

•

FJk

− = 0 (the system is critically damped)

•

FJk

− < 0 (the system is under-damped)

Our goal was to provide critically damped control to the turn of the robot.

The navread function in the navigation costatement determines the error

signal applied in the proportional control algorithm. The error is multiplied by a constant

K and converted to a signal to the plant, which causes motors to spin and the platform to

turn. Assuming that

and

are constant we manipulate

to get our system response

critically damped. We found that this was more difficult than imagined because, as it

turns out,

is a function of time

()

for our application.

Figure 17. Proportional Controller

A combination of proportional, derivative and integrative (PID) would be

the ideal method of feedback to use for a navigational system such as this. Hardware

issues and the limitations of the platform made PID control difficult. Due to the power

limitations of the Lemming chassis, a full power turn is required to ensure that the robot

will turn on any terrain, a feedback system, which would slow the turn as the robot

approached the desired heading, was therefore impractical. The time required to

Controller

(Navigate

Costate)

Plant

(Motors)

Feedback

(Digital

Compass)

Error

(Navigate

Costate)

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Proxim RangeLAN2 7920 Uživatelský manuál Strana 46