Robotics Sensor Exploration

2. Project Overview • Introduction • Frame Build • Motion • Power • Control • Sensors • Advanced Sensors • Open design challenges • Project evaluation

3. LESSON 06

4. LESSON 06 STARTER Sensor exploration Quick task:In groups, discuss each sensor and try to decide which description card matches which sensor. ? Bumper SwitchLimit SwitchLine TrackerUltrasonic Range FinderOptical Shaft EncoderLight Sensor

5. INTRODUCING SENSORS Learning objective: Develop an understanding of how inputs such as sensors help robotics to function. Work with a range of sensors to achieve a desired level of control and functionality. Consider – In the scenario shown right, the robot begins in the start zone (red) and needs to navigate towards an object, then needs to stop and change direction, continue forward, stop again, change direction, and move forward once more to navigate to the end zone (blue)With human interaction, we could use a controller to achieve this. But robots are not just human operated, but autonomous as well. Using sensors, we can achieve this outcome.

6. INTRODUCING SENSORS Solving this scenario It is actually very easy to achieve this goal, and in many different ways. Here is the best way…Ultrasonic range finder method1. Fit an ultrasonic range finder to the front of the robot. 2. Create a programme (code) that informs the range finder that once it receives a signal back from an obstacle close to it, the robot will stop.3. Once stopped, the code can instruct motors to move in opposite directions so that you achieve a zero radius turn (see right).4. Repeat this code but instructing the robot to stop and rotate left instead. 5. Launch the robot autonomously and watch it drive!Easy!!!

7. INTRODUCING SENSORS Analog vs DigitalAmong sensors, there are two main electrical “languages” spoken: Analog and Digital. You’ll have seen these on your cortex.Analog sensors communicate with the Microcontroller by sending it an electrical voltage along a wire. By measuring where the sent voltage falls between zero and a maximum voltage, the Microcontroller can interpret the voltage as a numeric value for processing. Analog sensors can therefore detect and communicate any value in a range of numbers.A line follower sensor, for instance, can communicate how bright a surface is by sending a zero voltage for total darkness, sending maximum voltage for a very bright light, or sending an in-between voltage for any other amount of light, depending on exactly how bright the surface is.

8. INTRODUCING SENSORS Analog vs. DigitalA weakness of analog sensors is that it is very difficult to send and maintain an exact, specific voltage on a wire in a live circuit. Digital sensors, on the other hand, can send signals very reliably, even in electrically “noisy” conditions. However, they do so by sacrificing the ability to indicate the entire range of values. Digital signals can only have one of two values: either HIGH or LOW.A digital sensor sends a voltage, just like an analog sensor, but instead of sending a voltage between zero and maximum, it will send only zero OR maximum. If the Microcontroller detects a voltage that is above a guaranteed Low or below a guaranteed High the results cannot be determined, it can be reported as a High or Low. It may seem like a terrible loss to only be able to indicate two values rather than a whole range, but in many situations, this is preferable. For instance, the Bumper Switch Sensor is a digital sensor. Since the purpose of the sensor is to detect whether something is pushing the bumper in or not, two values are all it needs to do its job.

9. INTRODUCING SENSORS “Bump” – this robot has been fitted with two bump sensors at the front and back of the robot. They are mounted onto two 3 inch stand-offs and wires are slotted into the cortex.Task: Propose what you think Bump does? Discuss at your table and write down your answer. Bumper Switch Sensor Signal: Digital Description: The bumper sensor is a physical switch. It tells the robot whether the bumper on the front of the sensor is being pushed in or not. Technical Info: Type: SPST switch (“Single Pole, Single Throw”) configured for Normally Open behaviour.

10. INTRODUCING SENSORS “Switch” – this robot has been fitted with two limit switches to the underneath of the robot chassis. These sensors brush the surface and trigger when pressed.Task: Propose what you think Switch does? Discuss at your table and write down your answer. Limit Switch Sensor Signal: Digital Description: The limit switch sensor is a physical switch. It can tell the robot whether the sensor’s metal arm is being pushed down or not. Technical Info: Type: SPDT micro switch, configured for SPST Normally Open behaviour.

11. INTRODUCING SENSORS “Line-o” – this robot has been fitted with a pair of line sensors under the front of the robot chassis. They lie side by side and will pick up changes in the surface colour and adjust the movement of the robot accordingly. Task: Propose what you think Line-o does? Discuss at your table and write down your answer.

12. INTRODUCING SENSORS “Sonic” – this robot has been fitted with two ultrasonic range finders, one at the front and one at the rear. Again they are fitted using 3 inch stand-offs, but this time wires from the sensor fit into the cortex labelled input and output. Task: Propose what you think Sonic does? Discuss at your table and write down your answer.

13. INTRODUCING SENSORS “Buzz-Light” – this robot has been fitted with a light sensor, on the front of the robot. Again it is fitted using a 3 inch stand-off, and a single input is plugged into the digital port.Task: Propose what you think Buzz-Light does? Discuss at your table and write down your answer.

14. INTRODUCING SENSORS Challenge 1 Design Challenge – design a Tumbler (on paper) that can do one of the following challenges. To do this challenge successfully you need to draw the sensors carrying out the task on the robot, including where they will be positioned to be triggered or to receive information.Challenge 1A robot that can drive down a tunnel until it hits a blockage, then return back to the entrance of the tunnel, provide a measurement.Challenge 2A robot that can detect gaps in very long (miles) animal zoo perimeter fence, stop at the opening, and sound an alarm to attract the zoo keepers to repair it.Challenge 3A robot that when loaded up with lit fireworks, can drive quickly to safe distance, stop, then let the fireworks go off, then return to the owner once the fireworks have stopped. Challenge 2 Challenge 3

15. CONSIDER YOUR SENSORS Which sensors?Here is a new scenario for you to consider. “The robot needs to travel across into the blue zone.There are buried landmines which will go off if drivenover too fast in its way. It needs to get to the blue zonein the quickest time possible.” First of all, what does the robot need to do to stay in one piece? Which sensor(s) are appropriate?What information would the sensors take in?How would the robot change its output? Answer: It needs to drive slowly over the land mines Answer: The limit sensors underneath would trigger by the landmine, which could single to the cortex to reduce the motor speed until the switch turns off again. The sensors would pick up the raised surface off the ground. The output would be slower motor drive.

16. LESSON 06 PLENARY As a class, let us consider the following questions?A. What do sensors do? (describe in detail)B. What can sensors not do for a robot?C. How do all sensors work?D. In the following areas, consider what sensors might be used for:- nuclear power plant- distribution of products across the UK using automation- the study of animals- sea rescue helicoptors- the farming industry- the military- in the kitchen

17. SUMMARY Learning objective: Develop an understanding of how inputs such as sensors help robotics to function. Work with a range of sensors to achieve a desired level of control and functionality. • Today you have: • Explored different types of sensors and how they create different forms of input. • Worked with different sensors to prepare for control of a robot. • Developed a wider knowledge of sensors and how they can be used in other contexts beyond robotics.