Introduction

Electric Wheelchair Permobil C500 uses two signals to control the speed of two wheels, thus control the movement of the wheelchair. These two signals are “Forward/Backward” (as “FB”) and Right/Left (as “RL”). The range for both signals is from 4.5 V to 7.5 V. In order to estimate the movement of wheelchair for research experiment purpose, we need to know the relationship between these two signals and the wheel speed (rpm).

We use 0.5 V as a interval to change these two signals from 4.5 V to 7.5 V separately, and measure the speed of wheel three times per combination to get the data. Then fit a linear regression model to get the coefficients. So we can set these two signals to estimate the path trajectory of the wheelchair.

Data Set

The column “FB” and “RL” are the input signal Forward/Backward" and “Right/Left”. The column “RWSpeed” and “LWSpeed” are the speed of right wheel and left wheel in rpm. Data set looks like this:

head(dataWheel)
##    FB  RL   RW     LW RWSpeed LWSpeed
## 1 4.5 4.5 2.16 -22.75    8.64     -91
## 2 4.5 4.5 2.16 -23.75    8.64     -95
## 3 4.5 4.5 2.16 -22.75    8.64     -91
## 4   5 4.5    3  -20.5   12.00     -82
## 5   5 4.5    3  -20.5   12.00     -82
## 6   5 4.5 3.16 -21.75   12.64     -87
str(dataWheel)
## 'data.frame':    147 obs. of  6 variables:
##  $ FB     : Factor w/ 8 levels "4.5","5","5.5",..: 1 1 1 2 2 2 3 3 3 4 ...
##  $ RL     : Factor w/ 8 levels "4.5","5","5.5",..: 1 1 1 1 1 1 1 1 1 1 ...
##  $ RW     : Factor w/ 92 levels "-10","-10.33",..: 65 65 65 76 76 77 90 91 90 51 ...
##  $ LW     : Factor w/ 104 levels "-0.3","-1.75",..: 24 25 24 19 19 23 12 13 11 4 ...
##  $ RWSpeed: num  8.64 8.64 8.64 12 12 ...
##  $ LWSpeed: num  -91 -95 -91 -82 -82 -87 -54.4 -54.8 -54 -42 ...

Plot