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Control and Robotics. Its all about the feedback. Sensing – environment, position, pose or attitude, obstacles, etc. Path Planning (traditional A/I) – given the environment, get to objective Control – How do you track the trajectory that you have generated.
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Control and Robotics Its all about the feedback
Sensing – environment, position, pose or attitude, obstacles, etc. Path Planning (traditional A/I) – given the environment, get to objective Control – How do you track the trajectory that you have generated Autonomous Mobile Platforms depend on:
Robotics in general Sensors in general Types of Sensors Filtering Issues Control in general PID (Proportional Integral Derivative Control) Example, 3 wheeled ground vehicle Outline
Robotics • Czech word Robota means compulsory labor. • “Rosum’s Universal Robots” written in 1920 by Czechoslovakian author Karel Capeck • Robotics: technology dealing with the design, construction, and operation of robots.
Robots According to Merriam-Webster: 1 a: a machine that looks like a human being and performs various complex acts (as walking or talking) of a human being; also: a similar but fictional machine whose lack of capacity for human emotions is often emphasized b: an efficient insensitive person who functions automatically2: a device that automatically performs complicated often repetitive tasks3: a mechanism guided by automatic controls
My Definition • Look at a Venn diagram of Mechanical and/or Electrical Hardware, Software, and Control Systems. • Robotics is the overlapping area at the center of the three Mechanical Robotics Software
What are some of the Issues? • Configuration • What mechanical scheme do you need to complete the mission • Example: UAV that deploys from a type “A” sonobuoy (36” long x 4.875” in diameter) • Example: Pipe Inspection must negotiate 90 degree bends, self contained, etc.
Navigation • How do you know where you are? • Outdoors • Underwater • In Space • Indoors • Underground
Guidance • Where do you want to go? • How fast do you need to get there? • Is there anything in the way?
Control • How do you get from where you are, to where you want to go? • What if something is not as predicted
Get the device to do what it is commanded Open Loop Control Feedback Control Must have a sensor Increases Disturbance Rejection Decreases Sensitivity to parameter variation Entire specialty of engineering Control Issues
Toilet Bowl Cruise Control Thermostat on House Missile Guidance System Mobile Robot Obstacle Avoidance Many, many more Examples of Control Systems
Dynamic Range Linearity Hysteresis Quantization Temperature Effects Bandwidth Sensor Issues
Power / Strength Linearity Hysteresis Quantization Temperature Effects Bandwidth Actuator Issues
Control System – PID • Proportional • Integral • Derivative
Proportional gain increases response speed, to much gain causes system to ring. Integral gain kills steady-state error, wind-up and/or too much gain can cause system to go unstable. Derivative gain adds damping and stability, but is sensitive to jitter and noise. PID Controllers
Don’t need to understand Controls or System to use PID. Start with pure Derivative control. Increase gain until system oscillates or you see over 50% overshoot. Go up to verge of ringing, back off by a factor of 2 or 4. Tuning PID Controllers
Start with Proportional gain, increase by factor of 8 to 10 until oscillation. If it is already oscillating, decrease by factor of 8 to 10. From verge of oscillation, back off by factor of 2 to 4. Tuning PID Controllers
Start with Integral gain very small, 0.0001 to 0.01. Increase until you get response you like. Be sure to implement anti-windup. If you have problems, play with sample rate. Tuning PID Controllers
