Question

You have been tasked with designing a digital controller for an Unmanned Ground Vehicle (UGV) which is essentially a robot that can navigate terrain autonomously. The application requires you to develop a robotic UGV that is capable of sensing radiation levels inside a nuclear power plant, where safety precautions do not allow personnel to enter with handhold sensors.

To get out of simple mazes, the ‘Right Hand Rule” algorithm is commonly used. Although this is certainly not an efficient path planning technique, it will always help your UGV find its way back to its home position, assuming that there is only one entry/exit point for the nuclear core facility. In the three-wheeled UGV shown in Figure 4.1, an antenna provides an input signal to the digital controller, R=1 when a wall is within 10-cm of the right-hand side of the vehicle, and R=0 otherwise. A bumper on the front of the vehicle also activates a switch, with B=1 when the UGV bumps into a wall and B=0 otherwise. The turn-right actuator causes the vehicle to turn right 10 degrees when TR=1, while the turn-left actuator causes the UGV to turn left 10 degrees when TL=1. Both TR and TL would most likely not be asserted at the same time. Figure 4.2 shows a simple state diagram of the state machine that can control the robot.

What are the inputs, outputs, and states of this digital controller?

Derive the state table from Figure 7.2

How many D flip flops are needed? Give a binary code to each state.

Derive the transition table

Answer 1

INPUTS:

SIGNALS: R=1---->WALL of 10 cm right hand side

                R=0----->when wall not present on right hand side

BUMPER:

         B=1---->bumps into a wall

        B=0------->when it doesnot bump

Directions

TR=1----->turns 10 degrees right

TR=0------->turns 10 degrees left

OUTPUT:

Go straight,Go left,Go right

STATES:

Home,Go straight,Go left,Go right

                    

TRANSITION TABLE:

STATE	INPUT	OUTPUT
HOME/TL',TR'	B'R	Go Straight/TL' ,TR'
GO Straight/Tl' , TR'	B	Go Left/TL TR'
GO Straight/Tl' , TR'	B'R	Go Right/TL' ,TR
GO Straight/Tl' , TR'	B'R	GO Straight/Tl' , TR'
Go Left/TL TR'	B	Go Left/TL TR'
Go Left/TL TR'	B'R	GO Straight/Tl' , TR'
Go Right/TL' ,TR	B	Go Left/TL TR'
Go Right/TL' ,TR	B'R	GO Straight/Tl' , TR'

STATE TABLE:

NAME	STATE DIAGRAM
HOME/TL',TR'	HOME/TL' ,TR' -----B'R---->   Go Straight/TL' ,TR'
GO Straight/Tl' , TR'	GO Straight/Tl' , TR' ------B---->Go Left/TL TR'
GO Straight/Tl' , TR'	GO Straight/Tl' , TR'---------B'R'--->Go Right/TL' ,TR
GO Straight/Tl' , TR'	GO Straight/Tl' , TR'-------------B'R------>GO Straight/Tl' , TR'
Go Right/TL' ,TR	Go Right/TL' ,TR--------B----------------->Go Left/TL TR'