Robotics Reprise piano movers problem Locomotion Lab session

Robotics Reprise: piano movers’ problem. Locomotion Lab session Homework: postings. Work on projects.

Complexity • Study of how long problem can take • Example: certain sorts may take up to square of N steps, for input size N; others take less: N*log 2 (N). • Binary search (dividing the search space) means that any search limited by log 2(N) steps.

NP complete problems • There is a set of problems for which there hasn’t been found a good solution. – Where good means doing in polynomial time. • Solutions for these problems can be checked in polynomial time. • Examples: graph coloring, traveling salesman, logical satisfiability • If one of these problems can be done, they all can be done.

The piano movers’ problem • Moving something, such as a robot with payload (what it needs to carry) through a space with obstacles. • Aka Motion planning • General problem is at least as hard as NP complete problems and may be harder! • One approach is to grow the obstacles while shrinking the robot and then go from corner to corner

Locomotion • What is the problem • What is requirement for stability – Static stability: capacity to return to standing if moved slightly – Dynamic stability: capacity while moving to return to (steady, desired) movement when pushed • What (where) is the control – What are the levels of control May have high-level goal supplied and then device achieves that goal through local action

Distinct problems/challenges: Navigate over a particular terrain • Level, smooth floors inside building – robot competitions – Manufacturing – Homes, hospitals, nursing homes, etc. • Streets – light payloads – Heavy/heavier payload: autonomous cars • In and out of streets & buildings – Rescue, detecting and disarming bombs, … • Ground (including moon, Mars, etc. )

More challenges • Combine travel over floor with climbing stairs in buildings (and other tasks such as climbing walls? ) • Imitate human locomotion – to replace [human] stuntman in movies – for testing of shoes and other gear • More ? ? ?

Different problem: Prosthetic limbs • Varying need to resemble somewhat is being replaced vs • Specialization for task – Sports limbs: Already controversy: double leg replacement allowed for longer legs http: //www. spectrum. ieee. org/jun 05/1217 Oscar Pistorius

Skiing • Trak III: – Remove leg and use outriggers – Critical issue is how to remove, protect stump and then re-attach limb

Skiing • Sit ski

Artificial limbs issues • Physical connection to body – Permanent? – Temporary but want long duration • Control connection to nervous system for control – Same – Other • Sensory input for performance of task

Hand Goal is for hand to be able to grasp without crushing object or letting it slip http: //www. newscientisttech. com/article/dn 1 0785 -robotic-hand-has-a-builtin-slipsense. html

Serpentine • Problems – Surgery – Disarm bombs, mines • Land or water – Rough terrain http: //www. primidi. com/2005/03/23. html

Note • Many of the experimental robots still are controlled teleoperator fashion • Though…some have complex distributed control systems

Mobile robot (Ralph Hollis) http: //www. msl. ri. cmu. edu/projects/ General goal: mobile, dynamically stabile agile to be personal assistant

Robots in Scansorial Environment (also Hollis lab) 6 legged climbing machine

Haptic devices Touch • contact • force • Note: may always be contact, for example, air, breeze. May need to quantify to distinguish.

Lab & Homework • Continue to work on building project • Postings