Smart Vehicles – Summary Leyla Nazhand-Ali, Ph.D. Assistant Professor IEEE member Michael Henry Graduate Student

This Talk We will review some topics that we discussed last week Autonomous vehicles Embedded microprocessors Programming an autonomous toy car Infrared sensors Square waves We will also talk about some new concepts: Closed loop control Design tradeoffs Decision Output Input Environment

Review: Why We Need Autonomous Vehicles?

Review: What are Autonomous Vehicles? A fully(semi)-autonomous vehicle can perform all (some) of its actions without any human control. Commercial vehicles already perform many automatic actions such as anti-lock brake, cruise control, lane departure warning, … Research vehicles have been able to drive themselves in urban-like areas.

Review: How is Autonomy Achieved? In a car, autonomy achieved similar to the way it is achieved by humans: First, we sense the environment Second, we process the data we collected through our senses (Yes, we do use our brains, at least sometimes!) Third, we act based on the decision we made sensors Controller (microprocessor) actuators

Review: Embedded Microprocessors Embedded microprocessors are the brains of real-time systems, which execute deadline-based tasks. They are usually smaller, cheaper, easier to program and develop, and consume less power compared to general-purpose microprocessors that are used in PCs. They are more reliable and failure resistant, which is crucial in embedded systems. You probably own dozens, maybe more than a hundred of them.

Review: State Table State tables are a way of making decisions. They are used for programming and are heavily used in designing digital hardware. For every possible input, specify the output. With the car, the input is the infrared sensors and the output is the motors. Good for problems with a small amount of input. Input (IR sensors) Output (Motors) Left Right White Forward Full Black Reverse Reverse Full Half Reverse Half Forward Half State table is a way of making decisions. For every possible input, specify the output. In this case, the input is the infrared sensors and the output is the motors. Good for problems with a small amount of input. Large amounts of input mean a lot of possible states the device could be in.

Review: Infrared Sensing Infrared (IR) is invisible light. IR sensor on car transmits IR light and measures how much bounces back. Black surfaces absorb a lot of light and reflect little. White surfaces reflect a lot of light. Based on how much is reflected, the processor can determine what surface the sensor is over. IR transmitter Black Surface IR transmitter White Surface

Other Sensors Similar to IR Sensor With IR sensing, you are sending out IR light and measuring its response. RADAR works by sending out radio waves and measuring the response. LIDAR and SONAR work like RADAR, but with light and sound, respectively. Barcode readers detect black and white, similar to your project, but they use visible light.

Review: Square Waves Square waves are used to feed the motor and make it turn. Period is the length of time it takes to complete one cycle. Frequency is how many times per second the wave completes a cycle. Duty Cycle is the ratio of time the wave spends being high and the period of the wave. It is usually expressed as a percentage. One cycle 5V 0V 1 / Period = Frequency Period 5V 0V 50% duty cycle 5V 0V 75% duty cycle

Other Wave Shapes Waves come in different shapes. Sound travels in a wave. AM radio uses changes in amplitude of the wave to send data. FM radio uses changes in frequency to do so. We use the same principles to use square waves for controlling motors. Voltage Sine Sawtooth Voltage Voltage Triangle Square 5V 0V

Closed Loop Control Control of the car can be simplified by thinking of the control as being a closed loop. The sensor provides data from the environment to the decision maker that starts an action, which in turn, affects the environment. Output using Actuator Input from Sensor 5V Decision Environment

Think, Pair, Share Activity Consider the automatic thermostat in your home, which is responsible to keep the temperature at a certain point. Come up with the closed loop that governs this system. Identify the input, the output, the decision maker and the environment variable. Decision Output Input Environment

Design Tradeoffs Most engineering problems involve design tradeoffs. Cost vs. Time: More expensive equipment will sometimes get the job done faster. Cost vs. Reliability: Expensive parts break less. Time vs. Quality: A project that’s rushed will not be as high of quality. Recognizing and controlling design tradeoffs is one of the most important tasks of an engineer.

Design Tradeoffs in Autonomous Vehicle Project In Task #3, there is a tradeoff between the “accuracy (quality)” of your solution and the speed. Drive the car too fast and it will frequently go off course and need correction. The fastest speed setting does not necessarily achieve the fastest completion time!

Design Tradeoffs in Autonomous Vehicle Project In some design problems, we have to sacrifice speed, quality and all other design objectives in order to achieve dependability and reliability. With task #4 we sacrificed navigation speed by using the right hand rule, but made the problem solvable and guaranteed reaching the destination. 2 1

Even Discoveries Involve Tradeoffs For the Infrared discovery activity, you tried to measure the reflectivity threshold of the sensors. Trying to do the measurement quickly by moving the car on the fastest setting results in a less accurate number. 80% 70% 60% 50% 40% 30% 20% 10%

Back to Autonomous Vehicles Everything you learned and applied is involved in the autonomous design process. Sensor input (IR sensors) Controlled output (Motors and Waves) Decision Making (State Tables) Reliability/Fault Tolerance (Embedded Systems)

Some other Thoughts By now you should have realized that the autonomous design process includes many diverse engineering topics. A successful design benefits from collaboration of many different fields.