Kinematics and Dynamics - Lab2.pdf

Kinematics and Dynamics of Mechanisms and Robot

Lab session 2 – SolidWorks Motion – Crank Slider

2011

Tran Thi Luyen – [email protected] Page 1

THE LABORATORY SESSION 2 FORDYNAMICS OF ME CHANISMS AND

ROBOTS COURSE

I. Lab Objective

Solidworks Motion is a simulation software package to analyze and optimize a mechanism,and it is embedded in the SolidWorks interface. It enables engineers to model 3D mechanicalsystems as “virtual prototypes” and can produce kinematics and dynamics result such asacceleration, joint reaction forces, and inertial forces.

The overall process of using SolidWrks Motion for analyzing a mechanism consists of threemain steps: model generation, analysis (or simulation), and result visualization, asillustrated in Figure 1. Key entities that constitute a motion model include servo motor thatdrive the mechanism for kinematics analysis, external loads (force and torque), force entitiessuch as spring and damper, and the initial conditions of the mechanism. Most importantly,assemble mates must be properly defined for mechanism so that the motion model capturesessential characteristics and closely resembles the behavior of the physical mechanism.

Figure 1 – General Process of Using Solidworks Motion

mailto:[email protected]



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II. Lab Assessment

The scoring structure mentioned here is for this Lab only; final Lab score will be combinedfrom all individual Lab scores.

If in group, score will be same for all students in group.

In case a student is absent, he (she) will not get the Attendance score. However, he (she) stillcan get other scores if he (she) submits (shows) the completion of assignments to the LabInstructor by the time students are working specified by the Lab Instructor. No group scoreis applied for absent student.

Criteria Score (percent)Attendance 20Completion of Lab session 2 80Total 100

III. Lab Setup

Convention: inches are used as units in this Lab session. To change the unit to inches for adocument, select Tools | Options | Document Properties | Units | IPS (inch, pound, second).

Use the Solidworks 2009 software to open the file Crank-Slider.sldasm in Lab 1. Choosefrom pull-downs menu: Tools à Add-ins and click Solidworks Motion in both boxes thenclick OK to active this software.

IV. User Interface of SolidWorks Motion

1. User Interface – Motion Manager




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User interface of the Motion is embedded in and identical to that of SolidWorks. The MotionManager is a separate window that is used to create and play animations as well as conductmotion analysis. When you open an existing assembly (or part) in SolidWorks, the MotionStudy tab (with the default name Motion Study 1) will appear at the bottom of the graphicsarea.

Figure 2

Motion Toolbar

Figure 3 – Motion toolbar




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The Motion toolbar shown in Figure 3 provides major functions required to create andmodify motion models, create an run analyses, and visualize result. As you move the mousepointer over button, a brief description about the functionality of the button will appear. Thebutton in Motion toolbar and their functions are also summarized in Table 1 1 with moredetails.

Table 1 1 The Shortcut Button in Motion Toolbar




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V. Using SolidWorks Motion

Click the Motion Study tab at the bottom of the graphics area to bring up the MotionManagerwindow. Double click the tab and rename the study Kinematic.

We will add a rotary motor to drive the crank and conduct kinematic analysis. Later we willadd a force for a dynamic simulation.

Adding a Rotary Motor

Click the Motor button from the Motion Toolbar to bring up the Motor window Figure 4.Choose Rotary Motor. Move the pointer to the graphics area, and pick a circular are definesthe rotation direction of the rotary motor as shown inFigure 5. You may change the

direction by clicking the direction button right under Component/Direction. Choose

Constant speed and enter 60RPM for speed. Click checkmark on the top of the dialog boxto accept the motor definition.

Figure 4




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Figure 5

Choose Motion Analysis for the study. Click the Motion Study Properties button fromthe Motion toolbar. In the Motion Study Properties dialog, enter 100 for Frame per second, andclick the checkmark on top. Drag the end time key to one second mark in the timeline area todefine the simulation duration.

Click Calculate button from the Motion toolbar to simulate the motion. After a shortmoment, you will see that the mechanism start moving. The crank rotates 360 degrees asexpected and the piston moving forward and backward for complete cycle.

Save and Reviewing Result

We will create four graphs for the mechanism: X-position, X-velocity, and X-acceleration ofthe piston; and velocity of mate Concentric 2 (between crank and rod).

Right Click on Piston from the Motion Manager. Choose Simulation Plot, the Result box willappear as Figure 7. Choose the Displacement/Velocity/Acceleration from the <Select category>,from the <select a sub-category> choose XYZ position, from the <select result component> chooseX Component. Click the checkmark on the top.




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Figure 6

Figure 7




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Figure 8 – X position of Piston

Repeat all steps to create the graphs: X-velocity, X-acceleration of the piston; and velocity ofmate Concentric 2 (between crank and rod).

Figure 9- X-Velocity of Piston.




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Figure 10- X-Acceleration of Piston.

Figure 11 – Angular Velocity of mate between crank and rod.




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Interference Check

Next we will learn how to perform interference check. SolidWorks Motion allows you tocheck for interference in your mechanism as the parts move. You can check any of thecomponents in your SolidWorks assembly model for possible interference, regardless ofwhether a component participates in the motion model. Using the interference check youcan find: All the interference that occur between the select components as the mechanismmoves through a specified range of motion, or the place where the first interference occursbetween the selected components. The assembly is move to the position where theinterference occurred.

Make sure you have completed a simulation before proceeding to the interference check.From the Motion Manager right click on the Crank- slider, choose Check Interference the boxwill appear as Figure 12. Select all components and click Find now button to start theinterference check.

After pressing the Find Now button, the mechanism starts moving, in which the crank rotatesa complete cycle. At the same time, the Find Interferences Over Time dialog box expands. Thelist at the lower haft of the dialog box shows all interference conditions detected. The frame,simulation time, parts that caused the interference, and the volume of the interferencedetected are list. Any interference occurs, we have to correct before save your mechanism.

Figure 12




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Creating and Running a Dynamic Analysis

The final analysis will be dynamic, where we will add the force (acting along the negative X-direction) to the piston for dynamic simulation. It will be more realistic if the force can beapplied when the piston starts moving to the left (negative X-direction) and can be appliedonly for a select short period. Therefore, the force is simplified as step function of 3 Ib, alongthe negative X-direction applied for 0.1 seconds. The force will be defined as a point force atthe center point of the end face of the piston.

Before we add the force, we will turn off the angular velocity driver defined in the previoussimulation. Right click on the Motor, choose suppress to off the motor.

Click the button Force to add the force with the step function as show in Figure 13.Click check mark on the top to accept the definition. We are ready to run simulation.

Figure 13

We will create four graphs for the mechanism: X-position, X-velocity of the piston; andReaction force of the pin of Rod and Piston.




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Figure 14 – X – Position of Piston

Figure 15 – X – Reaction Force of Concentric4

Save your model.

This manual is referred to Motion Simulation and Mechanism Design with SolidWorks Motionbook.


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Kinematics and Dynamics - Lab2.pdf