Animation Robot Roomba

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Project: Autonomous Robotic Vacuum Cleaner

Autonomous Robotic Vacuum Cleaner

Draft System Specification

Autonomous Robotic Vacuum Cleaner

Draft System Specification

Principle of Operation

The operation of the robotic vacuum is going to be based on retrieving data from an array of inputs that will tell the condition of the floor space around the vacuum. These inputs include sonar, touch sensors, and a digital compass. Each of these parts will be described in further detail further on later in the documentation. The data from these inputs will be fed into the chip(s) which through its software program will decide which direction the vacuum should move by sending the control signals out to the drive motors.

[pic]Figure 1. The initial block diagram for the Autonomous Robotic Vacuum Cleaner

Specification of the Blocks: There are 14 blocks in the block diagram of the robotic vacuum solution (Figure 1). The boxes in the figure indicate the action taken. Their functions are described below.

Sonar Conversion and Filter: The sonar block, representative of the sonar sensor network, is comprised of transmitting and receiving signals to detect objects. (Note: The suggested model that will be discussed is the SRF04 Ranger from Acroname Products).

After the battery supplies a voltage supply to the sensors, a trigger pulse input is needed to start the ranging. The processor will wait for an active low of the trigger pulse to come in. The sonar sensor will then transmit an ultrasonic signal at about 40 KHz in a burst of cycles. It will then raise its “echo line” on high, and then listen for an “echo”. The processor will start the timing when the echo line is raised. An echo line is a pulse whose width is proportional to the distance to the object and an echo will occur after it bounces off an object. As soon as the receiver of the sonar sensor receives an echo, the echo line will lower. But if nothing is detected the sensor will automatically lower after about 30ms. Thus, it is possible to calculate the range or distance by timing the pulse. The range for this system is approximately 3cm to about 3m. A wait time of at least 10ms is needed between measurements to allow it to recharge.

The output of the sensor will be filtered and then stored on the main chip used in the design. There will be approximately three to four sonar sensors. Each sensor will have an allocated address memory in which it stores their echo time return.

Touch Sensors: The touch block, representative of the touch sensors, operates in a much simpler fashion compared to sonar sensors. Touch sensors are somewhat analogous to light switches. When the sensor is “touched” or pressed, an electrical circuit located inside the sensor is closed. Thus, this permits the flow of electricity. Therefore, current flow will stop when the sensors are not pressed. A device then detects this current flow to recognize when the sensor is on or off.

There will be two to three touch sensors (bumper sensors). These are needed as a last resort obstacle detection in which the sonar did not detect for some reason. Output also will be stored in a separate space on the main chip. All sensors are used to both avoid obstacles and create a map of the environment.

Compass:
A digital compass will be used to assist the robotic vacuum in the direction in which it is going and the direction in which it needs to turn. The digital compass should have a digital output of the degree in which it is facing. Using the data fed into the chip, it can then decide if the vacuum should continue turning or if it is heading in the correct direction. The chip, with the help of this compass, can decide what signals to send to each motor.

Control and Reset
Control acts as the central processing unit of the robotic vacuum cleaner. It will be activated as soon as the user pressed the...
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