Motion analysis of Internal Geneva Mechanism

Aim:

• To create 3D models for driver and driven wheels.
• To perform motion analysis by rotating the driver wheel at 10rpm.
• Compare the contact forces with and without "Precise contact"
• Obtain the following plots
  • Contact force (between driving and the driven wheel) as a function of time.
  • Angular Displacement of the driven wheel

Introduction and Theory of Geneva Mechanism:

Geneva Mechanism

A mechanism that translates a continuous rotation into an intermittent rotary motion, using an intermittent gear where the drive wheel has a pin that reaches into a slot of the driven wheel and thereby advances it by one step, and having a raised circular blocking disc that locks the driven wheel in position between steps

Internal Geneva Mechanism

An internal Geneva drive is a variant on the design. The axis of the drive wheel of the internal drive can have a bearing only on one side. The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one, where the switch time is therefore greater than the time the driven wheel stands still.

Applications of Geneva Drive :-

1) The most common application of Geneva Drive is Movie Projectors.
2) Bank Note Counting Machines
3) Automated sampling machines.
4) Plotters – Plotter is a computer printer for printing vector graphics.
5) Wrist Watches.

3D Modelling and Simulation of Motion Analysis

1. Driven Wheel

2. Driver Wheel

3.Assembly

Motion Analysis Plots and Results:

For the Motion Analysis study, the following conditions to be applied

* Rotating motor is applied to the driver wheel with specified rpm and direction of rotation.

* All contacts are defined between the driver and driven wheels

* Simulation is then run for the required time length and results are saved.

Study 1: with 60 Frames per second for 10 rpm motor speed and without "Precise contact"

1.Contact forces between the Drriver and Driven wheels.

2. Angular displacement of the driven wheel.

3. Angular velocity of the driver wheel.

4. Angular velocity of the driven wheel.

Study 2: with 60 Frames per second for 10 rpm motor speed and with "Precise contact"

1.Contact forces between the Drriver and Driven wheels.

2. Angular displacement of the driven wheel.

3. Angular velocity of the driver wheel.

4. Angular velocity of the driven wheel.

Study 3: with 120 Frames per second for 20 rpm motor speed and with "Precise contact"

1.Contact forces between the Drriver and Driven wheels.

2. Angular displacement of the driven wheel.

3. Angular velocity of the driver wheel.

4. Angular velocity of the driven wheel.

Observation:

. When the "Precise contact" is enabled, the results are more accuarte and clear.

2. The magnitude of angular displacement in the driven wheel is directly proportional to the rpm of the driver wheel

3. The angular velocity of driver wheel remains same as constant rpm motor is attached to it.

4. The angular velocity of the driven wheel follows a cyclic motion with regular intervals.

Conclusion:

By the Motion analysis simulation, we can uderstand how multiple moving parts interact with each other and their environment and how mechanism systems move under the influence of forces.