Internal Geneva Mechanism
internal geneva mechanism
aim: to model and perform motion analysis with and without precise contact
introduction:
multibody dynamics is the study of the dynamic behavior of interconnected rigid or flexible bodies, parts which may undergo large translation and rotational displacement and movements.
the systematic movement of the dynamic behaviour of the interconnected bodies has held to a large number of important multibody formation in the field of mechanics. the simplest elements of the multibody system motion is described by their kinematic behaviour. the dynamic behaviour results from the equilibrium of applied forces and the rate of change of momentum.
the multibody dynamics related to the large number of engineering fields of research speciality in robotics and automobile vehicles.
theory:
motion in physics motion is a phenomenon in which an object changes its potion is mathematically described in terms of displacement, distance, velocity, acceleration, speed and time. the motion of a body is observed by the attaching frame of reference to an observer and measuring the change in a position of the body relative to the frame either change in time.
if the object is not changing relative to a given frame of reference the object is at rest, motionless.
types of motion
kinematics is the subfield of mechanics that describes the motion of points, bodies, and group of bodies without considering the forces that causes them to move as a field of studies.
dynamics is a branch of mechanics concerned with the studies of forces and their effects of motion.
constrained motion implies a restriction in the kinematical degree of freedom of one or more bodies.
motion analysis case setup:
2-D model
geometry
3D model
assembly of model
Mate in assembly
1 coincident mate: driver wheel axis - top plane of the assembly
2 coincident mate: driver wheel axis -right plane of the assembly
3 coincident mate: driven wheel axis - right plane of the assembly
4. coincident plane: front plane of driven wheel - front plane of the assembly
5. distance mate: 219.5mm: driven wheel axis - driver wheel axis
for motion analysis for 10 rpm keep 60 frames per second & for 20 rpm 120 frames per second
case 1
setup motor
constant speed 10rpm: driver wheel axis
contact
driver wheel: driven wheel
material: steel (dry)
setup plot and results
1. force: contact force : magnitude: driver wheel pin & driven wheel pin slot
2. displacement: angular velocity : magnitude: driver wheel
motion analysis setup
frames 60per second
with precise contact
plot and result 10 rpm with precise contact
the angular displacement of driver wheel
case 2
setup motor
constant speed 10rpm: driver wheel axis
contact
driver wheel: driven wheel
material: steel (dry)
setup plot and results
1. force: contact force : magnitude: driver wheel pin & driven wheel pin slot
2. displacement: angular velocity : magnitude: driver wheel
motion analysis setup
frames 60per second
without precise contact
plot and result 10rpm
the angular displacement of driver wheel
case 3
setup motor
constant speed 20rpm: driver wheel axis
contact
driver wheel: driven wheel
material: steel (dry)
setup plot and results
1. force: contact force : magnitude: driver wheel pin & driven wheel pin slot
2. displacement: angular velocity : magnitude: driver wheel
motion analysis setup
frames 60per second
with precise contact
plot and result 20rpm
the angular displacement of driver wheel
case 4
setup motor
constant speed 20rpm: driver wheel axis
contact
driver wheel: driven wheel
material: steel (dry)
setup plot and results
1. force: contact force : magnitude: driver wheel pin & driven wheel pin slot
2. displacement: angular velocity : magnitude: driver wheel
motion analysis setup
frames 60per second
without precise contact
plot and result 20rpm
the angular displacement of driver wheel
comparison of with precise contact force and without precise contact
with and without precise contact at 10rpm 60
with and without precise contact at 20rpm 60
observation
1. with and without precise contact force 10 rpm
while driver pin engages (enter) in pin slot the contact force in precise contact is rises to high force compared to without precise contact force.
as the pin slides in pin slot, the contact force and the driven wheel start to rotate in 90 degrees in total to perform output work
somehow the contact force in the precise contact the driver wheel pin exerts more force than without precise contact.
in the comparison between the precise and without precise contact force the difference in force is about 1000N
2. with and without precise contact force 20 rpm
in this case, all the observation are same except the contact force difference is higher than 10 rpm motor speed.
in 20 rpm driver wheel speed is higher than the 10 rpm driver wheel
the difference between them with precise contact force is double the without precise contact force
conclusion
1.as the rpm rises the contact force also rise with the speed of driver wheel
contact force and the speed of the drive wheel is directly proportioning to each other
2. in the motion analysis the contact between any two-body should be with precise contact will give more correct force to the more precise calculation in the factor of safety