Mechanism Introduction, Degree of Freedom, Type

Mechanism

1. Kinematic of Machine-1 Unit-1 Mechanism Dr. Nitin Upadhyay Department of Mechanical Engineering Madhav Institute of Technology & Science Gwalior

2. Ov e r v i ew

3. Introduction

4. Introduction Mechanism : Combination of rigid bodies (links) so shaped and connected that they move relative to each other for the purpose of transferring and transforming motion/forces from input(s) (actuator(s)) to an output Machine : A device that uses mechanism(s) to transform and transfer motion and force from a power source to perform some useful mechanical work

5. Key points

6. Motivation Mechanization and Automation : requirement of specialized mechanical devices (manufacturing, mechanical handling, assembly, painting, packaging)

7. Motivation Mechanization and Automation : requirement of specialized mechanical devices (manufacturing, mechanical handling, assembly, painting, packaging) Health-care : transfer aids and devices, physiotherapy, surgery

8. Motivation Synthesis and design : requires kinematic analysis Aim : Study kinematic analysis tools and techniques with applications

9. Transfer aids/devices Actuator throw, rates, forces

10. Surgical instruments Finger-grip motion range and sensitivity, forces

11. Landing gear Actuator throw and rate, force

12. Excavators Actuator throw and rate, reach, path, forces

13. R o b ots Exechon's Parallel Kinematic Machine (PKM) Source: www.twitter.com/ibonev/status/339217235300208640 Fanuc serial manipulator Source: www.dairyreporter.com Kinematic geometry (degree of freedom, rigidity), positioning, velocity, acceleration, work-space, motion planning, forces

14. Flight simulators Realistic body motion, actuator rates and forces CAE flight simulator Source: www.quora.com Stewart-Gough platform Source: Mechanics, J.L. Meriam and L.G. Kraige

15. Summary Introduction to subject of study Motivation and aim of study Examples with motion and force requirements

16. Ov e r v i ew Nomenclature and classification Types of links and kinematic pairs Kinematic chains and their classification

17. Nomenclature Kinematic chain : a combination of inter-connected links (rigid bodies)

18. Nomenclature Kinematic chain : a combination of inter-connected links (rigid bodies) Excavator

19. Nomenclature Kinematic chain : a combination of inter-connected links (rigid bodies) Exechon's Parallel Kinematic Machine (PKM) Source: www.twitter.com/ibonev/status/339217235300208640 Excavator

20. Planar and spatial chains ● Planar kinematic chain : all links move in parallel planes Excavator

21. Planar and spatial chains ● Planar kinematic chain : all links move in parallel planes Excavator Exechon's Parallel Kinematic Machine (PKM) Source: www.twitter.com/ibonev/status/339217235300208640 ● Spatial kinematic chain : link motion not restricted to a plane

22. Nomenclature Link classification : singular, binary, ternary, ...

23. Kinematic chain Classification of chains : closed, open and hybrid kinematic chains

24. Kinematic chain Closed chain : no singular link Open chain : at least one singular link; no closed chains Hybrid chain : combination of closed and open chains

25. Closed chain Exechon's Parallel Kinematic Machine (PKM) Source: www.twitter.com/ibonev/status/339217235300208640 Aircraft landing gear

26. Open chain Fanuc serial manipulator Source: www.dairyreporter.com

27. Hybrid chain Exechon's Parallel Kinematic Machine (PKM) Source: www.twitter.com/ibonev/status/339217235300208640

28. Nomenclature Kinematic pair : Connection between two links Example : hinge

29. Nomenclature Kinematic pair : Connection between two links Example : hinge Pair variable : quantifies relative motion

30. Nomenclature Classification : Lower pair or Higher pair

31. Nomenclature Classification : Lower pair or Higher pair Lower pair : Area contact

32. Nomenclature Classification : Lower pair or Higher pair Lower pair : Area contact Higher pair : Line contact or Point contact

33. Types of kinematic pairs

34. Revolute pair (R)

35. Revolute pair (R)

36. Revolute pair (R) Lower pair

37. Revolute pair (R) Lower pair One pair variable: 1 degree of freedom Powered R pair : Rotary motor

38. Prismatic pair (P) Lower pair One pair variable: 1 degree of freedom Powered P pair : linear motor, hydraulic and pneumatic actuators

39. Screw pair (H) Lower pair One pair variable: 1 degree of freedom Powered H pair : using rotary motor and ball screw (equivalent to powered P pair)

40. Cylindric pair (C) Lower pair Two pair variables: 2 degree of freedom

41. Spheric pair (S) Lower pair Three pair variables: 3 degree of freedom

42. Higher pair Point contact Two pair variables : 2 degree of freedom Form closed : slot

43. Higher pair Line/point contact Pair variables Form /force closed: slot /spring-loaded/gravity-loaded

44. Summary Nomenclature and classification Types of links and kinematic pairs Kinematic chains and their classification

45. O v e r v i e w Kinematic diagram Visualization of kinematic chains Examples

46. Kinematic diagram

47. Examples

48. Summary Kinematic diagram Visualization of kinematic chains Examples

49. Ov e r v i ew Degree of Freedom (DOF) calculation DOF of planar and spatial kinematic chains Examples

50. Degree of freedom (DOF) Minimum number of independent coordinates (variables) that need to be specified to fix the configuration of a mechanism

51. Degree of freedom (DOF) Minimum number of independent coordinates (variables) that need to be specified to fix the configuration of a mechanism One link of the chain is grounded

52. Degree of freedom (DOF): calculation

53. Degree of freedom (DOF) A mechanism must have at least 1 degree of freedom A structure has degree of freedom An over-constrained structure has negative degree of freedom

54. E x a m p les