Exercise Machine Repeated Assembly Analysis 1 ME-430 INTRODUCTION TO COMPUTER AIDED DESIGN Exercise Machine Repeated Assembly Analysis Pro/ENGINEER Wildfire 2.0 - MECHANISM Dr. Herli Surjanhata Servo Motors Servo motors are used to impose a particular motion on the mechanism model. Servo motors behave like motors, by forcing a specific type of motion to occur between two bodies in a single degree 2 of freedom. You can add a servo motor to a joint axis or a geometric entity, such as part planes, datum planes, and points. You use servo motors to impose a particular motion on a mechanism. Servo motors cause a specific type of motion to occur between two bodies in a single degree of freedom. You add servo motors to your model to prepare it for analysis. Servo motors specify position, velocity, or acceleration as a function of time, and can control either translational or rotational motion. For example, a servo motor starts in a specific configuration. After one second, another configuration is defined for the model. The difference between the two configurations is the motion of the model. By specifying your servo motor's function, such as constant or ramp, you can define the motion's profile. You can select from several predefined functions, or input your own function. You can define as many servo motors on an entity as you like. Note: If you select or define a position or velocity function for your servo motor profile that is not continuous, be aware that it will be ignored if you run a kinematics or dynamic analysis. However, you can use a discontinuous servo motor profile in a repeated assembly analysis. When you graph a discontinuous servo motor, Mechanism Design displays messages indicating the discontinuous points. You can place servo motors on joint axes or on geometric entities such as part planes, datum planes, and points. You can use the following types of servo motors: • Joint Axis Servo Motors—Use to create a well-defined motion in one direction. • Geometric Servo Motors—Use to create complex 3D motions such as a helix or other space curves. Force Motors You use force motors to impose a particular load on a mechanism. You can create force motors for your mechanism if you have a Mechanism Dynamics Option license. Force motors cause a specific type of load to occur between two bodies in a single degree of freedom. You add force motors to your model to prepare it for a dynamic analysis. Force motors cause motion by applying a force on a translational or rotational joint axis. You can place force motors on joint axes. You can define as many force motors on a model as you like. You can turn force motors on and off within the definition of each dynamic analysis. 3 Geometric Servo Motors If you select points or planes to define the servo motor, you are creating a geometric servo motor. Use geometric servo motors to create complex 3D motions such as a helix. If you select Point or Plane, you must also select a point or plane as a reference. If you select a point for the reference entity, you must also select a motion direction. You can create the following geometric servo motors: • plane-plane translation servo motor • plane-plane rotation servo motor • point-plane translation servo motor • plane-point translation servo motor • point-point translation servo motor REPEATED ASSEMBLY ANALYSIS Repeated Assembly analysis was called Kinematic analysis in previous releases of Mechanism Design. It is a series of assembly analyses driven by servo motors. Only joint axis or geometric servo motors can be included for repeated assembly analyses. Force motors do not appear in the list of possible motor selections when adding a motor for a repeated assembly analysis. Note: If you edit an analysis that you created as a Kinematics analysis in a previous release of Mechanism Design, the definition will now specify it as a Repeated Assembly analysis. A repeated assembly analysis simulates the mechanism's motion, satisfying the requirements of your servo motors profiles and any joint, cam-follower, slot-follower, or gear-pair connections, and records position data for the mechanism's various components. It does not take force and mass into account in doing the analysis. Therefore, you do not have to specify mass properties for your mechanism. Dynamic entities in the model, such as springs, dampers, gravity, forces/torques, and force motors, do not affect a repeated assembly analysis. Use a repeated assembly analysis to study: 4 • positions of components over time • interference between components • trace curves of the mechanism's motion Force Motors You use force motors to impose a particular load on a mechanism. You can create force motors for your mechanism if you have a Mechanism Dynamics Option license. Force motors cause a specific type of load to occur between two bodies in a single degree of freedom. You add force motors to your model to prepare it for a dynamic analysis. Force motors cause motion by applying a force on a translational or rotational joint axis. You can place force motors on joint axes. You can define as many force motors on a model as you like. You can turn force motors on and off within the definition of each dynamic analysis. Download the Component Parts for Assembly In a system window, create a new directory and download the zip file exercise_machine.zip. Unzip the file, and set the working directory. Create A New Subassembly Called raiser_subasm.asm The raiser_subasm.asm is consisted of raiser.prt and raiser_shaft.prt 5 Click on Enter the name raiser_subasm. OK Open raiser.prt, and assemble it at default location – click . OK 6 Open raiser_shaft.prt, and click on Connect tab. Create Pin type connection as the following: Axis alignment: Axis of the raiser_shaft (A_2) is aligned with the axis (A_3) of the hole on the raiser. For Translation constraint, pick FRONT datum plane of the raiser_shaft, and then pick FRONT datum plane of the raiser. OK. Save the raiser_subasm.asm 7 Create A New Subassembly Called pedal_left_subasm.asm The pedal_left_subasm.asm is consisted of pedal_left.prt and roller.prt 8 Click on Enter the name pedal_left_subasm. OK Open pedal_left.prt, and assemble it at default location – click . OK. 9 Open roller.prt, and click on Connect tab. Create Pin type connection as the following: Axis alignment: Long axis of the roller (A_1) is aligned with the axis (A_2) of the left cut (half cylinder cut) on the pedal_left. For Translation constraint, pick FRONT datum plane of the roller, and then pick FRONT datum plane of the pedal_left. OK. Save the pedal_left_subasm.asm [...]... plane of the pedal_right OK Save the pedal_right_subasm.asm 12 Create A New Assembly Called exercise_ machine. asm The complete Mechanism Design Model of exercise machine will be created in this step The total assembly will be consisted of components and subassemblies created in the previous steps Click on Enter the name exercise_ machine OK 13 Open chasis.prt, and and assemble it at default location – click... with A_2 axis of ramp.prt For Rotation constraint, select TOP datum plane of the roller.prt, then select the top surface of the ramp OK 28 Assemble cover.prt to Rear Part of the Machine Open cover.prt, and assemble it to the machine as shown in the figure below 29 Mate the bottom surface of the cover with the top surface of the bottom part of the chasis – see figure below Align the right surface of...Create A New Subassembly Called pedal_right_subasm.asm The pedal_right_subasm.asm is consisted of pedal_right.prt and roller.prt Click on Enter the name pedal_right_subasm OK 10 Open pedal_right.prt, and assemble it at... cover with the right surface of the bottom part of the chasis – see figure Align the front surface of the cover with the front surface of the bottom part of the chasis – see figure 30 31 Transfer the assembly model to Mechanism Applications -> Mechanism Test the Connections This model has been fully assembled as a MDX (Mechanism Design Extension) model with the appropriate connections To test these... that all MDX connections have been lined up according to their definitions and constraint references 32 Click on Yes Note: If Yes is selected, the bodies in the model will be repositioned such that the assembly connections have been aligned according to their definition and constraint references If No is selected, the bodies in the model are returned to their original position Select from the toolbar... erratic For this model type it would be prudent to lock one body while moving the rest In this instance we will lock raiser.prt so we can independently observe the motion of the other components of the assembly without moving the aforementioned part 33 Select the Constraints tab in the Drag dialog box Select the Body-Body Lock Constraint icons Select chasis.prt as a reference part for locked body and . Exercise Machine Repeated Assembly Analysis 1 ME-430 INTRODUCTION TO COMPUTER AIDED DESIGN Exercise Machine Repeated Assembly Analysis. REPEATED ASSEMBLY ANALYSIS Repeated Assembly analysis was called Kinematic analysis in previous releases of Mechanism Design. It is a series of assembly