Project Overview  Introduction  Clawbot Build  Design Modification  Design Development  Programming  Sensors  Advanced Sensors  Open design challenges  Project evaluation

LESSON 06

LESSON 6 STARTER Key words: Programmable, environment, design, manufacturing and application Learning objective: Apply a range of sensors and propose their application for the robot. Consider the wider context of using sensors for human operated robotics. Redevelop a robot to improve its design and function. These three sensors are going to add some functional features to your clawbot. What are their names and what do they do? Once you have identified this information, your task is now to fit them and programme them to work on your clawbot.

Modifying the Clawbot Task 1: Modifying the build of the clawbot build as per below to develop its assembly In this part of the lesson your task is to: 1. Fit a bump sensors to the back of the clawbot 2. Fit a limit switch to the top of the tower behind the arm 3. Fit an ultrasonic range finder to the front of the clawbot Bump Sensor Fit the bump sensors by removing a 20 hole bar from the Clawbot, straightening it, and attaching it to the back of the frame behind the wheels. Use the bump sensors and long screws to tighten everything together. Limit Switch Fit the limit switch by first removing the second 20 hole bar from the Clawbot, and bending it into a frame around the top of the tower. Fit the limit switch and bend its trigger until it can hit the arm as it rises. Ultrasonic Range Finder Fit this at the front of the frame using 2 stand-offs and screws. Centre it as best possible.

Modifying the Clawbot Things to check are: 1. There is clearance for the bump sensors to not only hit but press in front of the wheels. 2. The limit switch triggers when you move the arm back against it. 3. The ultrasonic range finder is pointed forward and central to the robot. Connecting the wires Connect each of the sensors as shown: 1 = limit 2 = bump 3 = bump 4 = ultrasonic out 11 = ultrasonic in Check before you programme: Your robot should look like this 

Modifying the Clawbot Task 2: Create a programme for one Bump Sensor… (see “shut down code” example file) Step 1: Create a while loop Step 2: Add the Bump sensor & any code that makes the robot work. Step 3: Add an IF statement Step 4: In the IF statement, add in what the robot will do autonomously when the bump has been hit, using motor control and wait. Step 5: Add the Bump Sensor in again. Notes:For the While statement you need to enter the following into the box Bump ==1 For the Bump sensor before the IF, you need to read sensor position 3 For the Bump sensor in the IF sequence you need to read sensor position 3 In the Variables there is a “Bump” created as an unchar signed component

Modifying the Clawbot Task 3: Add the second Bump sensor to the programme… (see “shut down code 2” example file) Step 1: Add to the While state an or symbol between closed brackets that contain: (Bump==1) | (Bump2==1) Step 2: Add a second Bump Sensor below the first Step 3: Copy and paste the first IF statement, and change it for the second sensor. Note: In the variables, you need to add a Bump 2 sensor again as an unchar signed component

Modifying the Clawbot Task 4: Create a programme to stop the arm going too high… 1. Having learnt in lesson 5 the basics of creating a programme and sensor trigger, your test is to see if you can create a programme to stop the arm if it touches the arm as it rises up. 2. Using this arrangement from the previous programme, but swapping over the sensor from a bump to a limit switch is the first step. 3. You next need to fit into the IF and ELSE statements what you want the arm to do when it has or has not triggered the limit switch. Remember the limit is sat behind the arm, and plugged into position 1 on the digital input section of the cortex.

Modifying the Clawbot Task 5: Create an autonomous programme for the Ultrasonic range finder As you work through this Clawbot project you might be considering the VEX Robotics Competition. For this there is a 15 second autonomous period before operator control takes over. In this task you are going to create an autonomous programme using the ultrasonic range finder and evaluate how it is working. Copy this programme into an autonomous programme and test it out. (ultrasonic range finder example file) Note: Take out the other sensors, and move the Ultrasonic out to position 1, leaving the Ultrasonic input in position 11. In the variables, you need to create: Type = int Name = Ultrasonic

Modifying the Clawbot Upload your file: Plug your Clawbot into the laptop and upload the file to the cortex. Once you have uploaded the file you want to test out, turn your robot and controller pair on with the wireless keys attached, and test out the functionality of the robot. Task 6: Establish the functional performance of each sensor programme before attempting to build them into one single programme file. Consider Analysing how the sensors perform individually in order; Bump switches, Limit switches, Ultrasonic Range Finder. Describe what each does in detail and how. Consider how these sensors could be employed for a different use, or for a better use. List these in your engineering notebook.

LESSON 6 PLENARY As a class, let us consider the following questions? A. What is the benefit of adding sensors to the clawbot? B. What would the human operator need to do to replicate the role the sensors do? C. How could the ultrasonic range finder be confused or tricked? D. How are bump sensors and limit switches different from sensors like the ultrasonic range finder?

Summary Today you have:  Learnt how to rebuild your clawbot to improve its design using sensors  Developed a unique programme to support the robots operation  Propose how sensors support good robotics design and better human and robot interaction Learning objective: Apply a range of sensors and propose their application for the robot. Consider the wider context of using sensors for human operated robotics. Redevelop a robot to improve its design and function.