You have been tasked with designing a digital controller for

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

HOM B\'R UGV 8\'R TTR B. BR Digital TL Controller TR Go LEFT TL TR TL TR Figure 7.1: Three-Weeled UGV. the UGV. Figure 7.2: State diagram of

Solution

B and R are input to the sytme

TL and TR are output to the sytem

HOME,GO_stright,GO_left,Go_right are the states of this digital controller.

Total 4 states are there so we need 2 D flipflops(2ⁿ=Nof of states, where n is no of flip flops)

State Table:

Assign

Home=00;GO_stright=01;Go_left=10;Go_right=11

Transient Table:

INPUT	PRESENT STATE	NEXT STATE	OUTPUT
B	R	TL	TR
0	0	HOME	HOME	0	0
0	1	HOME	GO_stright	0	0
1	0	HOME	HOME	0	0
1	1	HOME	HOME	0	0
0	0	GO_stright	Go_right	0	0
0	1	GO_stright	GO_stright	0	0
1	0	GO_stright	GO_left	0	0
1	1	GO_stright	GO_left	0	0
0	0	GO_left	XX(Don’t Care)	1	0
0	1	GO_left	GO_stright	1	0
1	0	GO_left	GO_left	1	0
1	1	GO_left	GO_left	1	0
0	0	Go_right	XX(Don’t Care)	0	1
0	1	Go_right	GO_stright	0	1
1	0	Go_right	GO_left	0	1
1	1	Go_right	GO_left	0	1