Internal Geneva Mechanism

REPORT ON MOTION ANALYSIS OF INTERNAL GENEVA MECHANISM

AIM – To conduct the motion analysis of the internal Geneva mechanism, generate and explain the plots for the given conditions.

BODY OF THE CONTECT

• Creating parts of the assembly.

The first step to carry out the motion analysis is to model the parts of the assembly in order to perform motion analysis on it

The internal Geneva mechanism has two basic parts in it namely driving wheel and driven wheel. Driving wheel is the part that initiates the rotation. It act as input of the motion. The output of intermediate rotation we get on driven wheel.

• Driving wheel

• Driven wheel

• The second step is to make assembly of internal Geneva mechanism.

• Carry out motion analysis

Once the assembly of the internal geneva mechanism is completed the next step is to perform the motion analysis on it. Motion Analysis is a process that is been carried out to study the performance of the any physical system in actual condition.

• The plots generated after motion study

• Contact force vs time without precise contact

Given conditions

Input rpm = 10 rpm

precise contact = off

This plot shows the magnitude of the contact force with respect to time. The entire motion analysis is for 10 secs. Hence the plot show results upto 10 secs. Here in this plot the precise contact option is not been selected hence the generated contact is calculated approximately using the geometry of many sided polygon. Without precise contact the plot that I got is quite sharp. Without selecting the precise contact option the solution that we get is approximate which is less accurate but it can solve the problem in less possible time. So initially when there in no contact is initiated the graph shows 0 contact force but once the contact is initiated there is a sudden rise in the force is been shown in the graph it goes around 3.25 newtons at that point. Once the motion is initiated we don’t see much fluctuation in the force during entire cycle.

• Angular displacement vs time without precise contact for driven wheel

Given conditions

Input rpm = 10 rpm

precise contact = off

This plot shows the angular displacement of driven wheel with respect to time for this I had selected one of the slotted face of the driven wheel. The graph shows the angular displacement of the driven wheel initiates at near about 4 degrees which represent the initial position of the selected face. Then we see a certain rise in the graph that shows the driven wheel rotates in opposite direction which is counter clockwise direction until proper contact in initiated by both the parts. Once the driving pin properly slides into the slot the driven wheel starts to rotate in clockwise direction. Here the portion of the graph that rises upwards shows the motion of the wheel in counter clockwise direction and the portion that propagate downward shows the clockwise rotation of the driven wheel. Approximately at time span of 5 to 7 secs it is observed that is wheel again rotates in the opposite direction that is due to the inertia of the wheel as during this span the driven wheel is not in contact with the driving pin hence it does not have any support so the gravity tries to rotate it in opposite direction. Since precise contact option is not been selected during this study the plot that we get is quite sharp.

• Image of precise contact selection

• Contact force vs time with precise contact

Given conditions

Input rpm = 10 rpm

precise condition = on

The above graph shows the plot of contact force with respect to time with selection precise contact option. When we select the precise contact option the system calculates the contact by using the equations that represent the solid bodies hence computed contact is analytically correct. This helps in increasing the accuracy of the solution and we also get the smooth plot as compare to the same plot without precise contact. Initially for few microseconds the graph shows 0 N contact force then the first contact force reading is been shown by the graph once the contact is been generated which is approximately around 8.2 KN force. This value of the contact force is greater than the value of contact force that we got without precise contact. Since we have used precise contact option we can say that this value of 8.2KN is more accurate than the same value without considering the precise contact. This graph shows that there are two points within 10 secs at which the driving pin makes contact with driven wheel at approximately around 0.5 sec and 6.5 sec. The intensity of the force at the initial contact is always greater than the intensity after the motion is been initiated.

• Angular Displacement vs time plot with precise contact.

Given conditions

Input rpm = 10

precise contact = on

The above graph shows the plot of Angular displacement of driven wheel vs time plot with considering the precise contact option. There is no much difference in the plot than plot without precise contact but the plot that is computed with considering the precise contact is more smooth as compare to the plot without precise contact that shows how the precise contact option can bring the uniformity to the plot along with increasing the accuracy of the solution.

• Angular velocity vs time plot

Given conditions

Input rpm = 20 rpm

precise contact = on

The above graph shows the plot of Angular velocity of the driving wheel with respect to time. The angular velocity at the initial state can be obtained from the graph which shows approximately around 6 deg/sec. This angular velocity goes on increasing to 12 deg/sec upto 5 secs after that the angular velocity remains constant till the end of the cycle.

• CONCLUSION = In order to get more accurate solutions it is feasible to use the precise contact option while performing the motion analysis for a given application.