Internal Geneva Mechanism
AIM:- MOTION ANALYSIS OF INTERNAL GENEVA MECHANISM
- Basic:-
Geneva drive or Maltese cross is a gear system that translates continuous rotational motion into intermittent rotary motion. the difference between the Geneva Drive modes and the other gears is that the Geneva Drive dentist has unusual teeth. Unlike conventional gears, the communication between the driven part and the driving part is not continuous and the flow of the effect occurs from time to time. Geneva Drives operates by having a driving part, or wheel, to communicate with a part driven periodically. The number of speakers that the driven section has and the speed at which the driving part rotates to determine the frequency and distance of travel. There is a high part in the steering wheel that keeps the driven part in shape until the next transition is completed. The external Geneva dive is the most common type, although there are some differences in composition. An external hard drive can be built to withstand high levels of stress and is usually more durable and durable than other variants.
Fig.1 Internal Geneva drive Fig. 2 External Geneva drive
Inside the Geneva Drive it has a steering wheel under the steering wheel, and the driving part is usually smaller than the steering wheel. the axis of the steering wheel of the internal drive can have a side effect. The angle at which the steering wheel must accelerate to make the one-step rotation of the steering wheel is always smaller than 180 ° on the external Geneva drive and remains greater than 180° on the interior, where the rotation time, therefore, is greater than the time when the steering wheel is stationary.
- Objective:-
- To create 3D models for driver and driven wheels.
- Perform motion analysis by rotating the driver wheel at 10rpm.
- Obtain the following plots:
- Contact force (between driving and the driven wheel) as a function of time.
- Angular Displacement of the driven wheel.
- Compare the contact forces with and without "Precise contact."
- Showing image for precise contact selection.
- Export the results that we get to Excel and make the plots over there.
- Procedure:-
In order to do a detailed analysis of Geneva's internal mechanism first we need to design the 3D components of the Geneva machine. So, to do that we will build each component in Solidworks. i.e. the first part is the driving wheel and the second part is the driven wheel based on the following 2D diagram.
fig. 3 2D Drawing of Diver and Driven Wheel.
To do part design, open Solidworks software > choose a new option > choose a part design option. Before designing part we need to verify our unit system which is as MMGS (i.e. Millimeter, Gram, Second).
3.1 Driver part:
We will build our first part which is driving wheel based on 2D drawing. First select the front plane and select the drawing option, drawing a circle on Axis 420 inches in size, similarly drawing a small circle with a diameter of 40 millimeters and a distance of 160 mm from the center.
After completing 2D sketching we will use the Extrude option. To make a 2D drawing 3D. Add a large circle and a small circle about 20 mm and 40 mm respectively.
The end result of the first part is as shown below.
fig. 4 Driving Wheel
After completing the driver part we are going to save it as a name of driving Wheel on our computer.
3.2. Driven part:
We will build our first part which is Driving wheel based on 2D drawing. first select the front plane and select the drawing option, drawing a circle on Axis 420 inches in size, similarly drawing a small circle with a diameter of 40 millimeters and a distance of 160 mm from the center.
After completing 2D sketching we will use the Extrude option. to make a 2D drawing 3D. Add a large circle and a small circle about 20 mm and 40 mm respectively, the end result of the first part is as shown below.
fig. 5 Driven Wheel
After completing our driven part we are going to save it as a name of driving wheel in our computer.
3.3 Assembly Design:
To perform the motion analysis we will combine the components we have previously designed. For the sake of convenience we use the name of part 1 of the steering wheel and the name 2 of the steering wheel part. first, we will open a new file and select the assembly by taking that unit
Now, we're introducing two parts to the meeting.
Note: - The first part to be imported is always resolved to release to right-click on Part-1 and then click on the float option, we can now move our part to our required line. after that, we will use the partner option to trick or split.
we will select a temporary Axis that appears simple in assembly. now we see more axes in our parts. we prefer the front-plane of part-1 and assembly and we prefer uniformity. one way to do that is that we can select a partner option when we are at a meeting and select a pre-conference flight and a pre-part 1 flight.
select Center axis for part 1 and then considering the assembly plane of the assembly, likewise, we will match the axis of the Part 1 center to the top assembly area.
now we see that our part 1 is completely suppressed it can only work in a circle on its base.
again, we'll press for our second part. to do that we look at its Axis at the right angle of junction and reduce it. now we can see that our part corresponds to part 1 but it still needs a fair cut. that's why we're going to find the middle distance and part 2 that we don't know, that's why we're taking the right distance between the parts.
fig. 6 Assembly
3.4 Simulation and Analysis:
To perform simulation and analysis (e.g. motion analysis) we will select the Solidworks movement option from Solidworks Add-Ins. we now see that the motion analysis option shown below in the Solidworks window.
To get around the steering wheel we will assign the motor to the steering wheel. to make that choice in the vehicle selection on the movement test and select part 1 of the axis. after that, we will assign a solid physical contact by selecting the contact option and selecting part 1 and part 2. from the menu we can provide information on the components.
To analyze multiple parameters, we can use the structure option in motion analysis, the results of the drop are as follows.
3.4.1 Analysis at 10 RPM:
- Contact force:
The plot of contact force between driving and the driven wheel as a function of time is as follows.
The contact force is the same in magnitude in a constant interval of time.
- Angular Displacement of the driven wheel:
From plot-2 we can see that the angular velocity of the driven wheel is initially decreased slightly after that we can see small sudden increment and gradual decrement overtime respectively.
- Contact forces with Precise contact:
The contact force is continuously changing in a given time interval and we can calculate each and every point of a jerk as shown in the plot The Precise Contact gives a more accurate result.
3.4.2 Analysis at 20 RPM:
- Contact force:
from the plot of contact force at 20 rpm and by comparing with contact force at 10 rpm, we can say that by increasing rpm of the motor we can reduce the jerk which will discuss in the "Error and error elimination section".
- Angular Displacement of the driven wheel:
From plot-5 we can see that gradual decrement and sudden increment in the angular Displacement at 20 rpm. This trend is constant throughout the interval.
- Contact forces with Precise contact at 120 FPS:
from the plot of contact force with the use of precise contact, we can say that the precise contact gives us more clear results. also, we can see small jerk also which is induced in operation.
3.4.3 Angular velocity of Driver wheel at 20 RPM :
As we saw in plot-7 the angular lid is at its lowest point at the beginning of the rotation. As the rotation of the steering wheel increases the angular velocity also increases but, we can see that the continuous line in structure-7. The continuous line shows that when inserting a rotator / key into the slot of the steering wheel the angular wheel of the wheel drive remains constant.
3.4.4 Comparing the contact forces with and without Precise contact:
Comparison of the contact forces with and without the 'Precise Contact' , we can conclude that the exact contact gives more accurate results as we can see that the plots. We can also see small changes in the plot with the help of precise contact.
3.4.5 Surface selection for Contact force:
Here, our surface selection for the contact force is based on the direction of rotation of the drive and driven wheel. In our view, both our drive and the driven wheel rotate in a clockwise direction and gravity acts on the y-axis. Therefore, we selected the surface of the rotator in the drive wheel and the surface of the driven wheel which is in contact with the rotator in the clockwise direction as shown below.
fig. 6 surface selection for contact force
- Error & error elimination:-
The most common error we can find during motion analysis is a jerk.
The original cause of the jerk is due to improper alignment of the steering wheel and steering wheel. This can cause serious damage to a real-life situation. So to avoid this error we need to align the drive with the steering wheel by adjusting the mid-range distance between them.
The second cause of the jersey is due to the low rpm of the car. Because gravity acts on a steering wheel a small variation instead of a steering wheel occurs. therefore, the key cannot be inserted into the slot smoothly. To avoid that we can either increase the car's rpm or set our assembly line in such a way that the force of gravity is zero.
Note: - Always keep in mind the unit plan while performing the component design and assembly.
- Result and Conclusion:-
5.1 Final Output:
5.2 Conclusion:
When the driver tries to enter the slot of the steering wheel it is facing the jersey. as the entries are not smooth. Thus, we can see from the structure, the sudden increase in contact strength at the slot entry. As we increase rpm angular displacement also increases.
- Reference:-
https://en.wikipedia.org/wiki/Geneva_drive
link of files:
https://drive.google.com/drive/folders/184ot42vKM6_ZUtV0Yc2IMMwn-Rl3z3fb?usp=sharing