08.2 - Design Process and Kinematic Analysis

Kinematic Analysis

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Physical Prototype

This prototype serves to demonstrate a successful proof-of-concept for the motion and mechanism of our horse race simulator, including both the linear motion of the horse along the track, as well as the rotational motion of the 4-bar mechanism in the horse itself. This physical prototype helps us visualize the kinematics of the 4-bar mechanism and validate the movement of the output links and joints, as plotted in our motion analysis program. The prototype is manually powered, where we actuate the input link which fully rotates about a gear which will ultimately translate into linear motion along a rack. We wanted to validate that the input link was Grashoff and test for play/friction in the joints in the full range of motion. We also wanted to iterate on how the rotational input link would roll across the rack, gauging how we can further refine the gear and rack size, as well as the gear teeth to achieve smoother motion.

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Figure 6: Protoype of Horse Racing Simulator

Moving forward from this prototype, we intend to perform the following:

• Integrate a sproket and chain to drive the inout gear along the rack

• Incorporate bearings to reduce friction and increase robustness at the joints

• Develop the electronics and integrate with the mechanical components to actuate motion electronically

• Add another horse and write the Arduino program to start the game and end with an unpredictable horse race outcome, by controlling the motors torque output of the horses.

• Scale up the models and add aesthetic elements

Iteration Documentation

During the intial design phase, we developed a makeshift model to help us visualize the range of motion that our mechanism would need to emulate the horse’s gallop. The links were made out of cardboard, held together at the joints using ush pins. We at first developed a 5-bar linkage, however, we pivotted to a 4-bar linkage to achieve a more smiple robust 1 degree of freedom mechanism, driven by one rotational output link to initiate the gallop.

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Figure 7: Iteration 1 (5-Bar Cardboard Linkage)

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Figure 8: Iteration 2 (4-Bar Cardboard Linkage)

Upon initial testing of these iterations, we discovered that the links would interfere with the ends of the push pins, thereby impeding the full range of motion of the mechanism. We addressed this by implementing spacers at each of the links that allowed enough clearence for each link to rotate without interference.

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Figure 9: Video Demonstration of 4-Bar

After refining our original mockup, we began developing a CAD model using our calculated link lengths and detailed motion analysis to actuate our desired output link behavior. The model was also mated in to the rack in an assembly which could emulate the motion of the 4-bar linkage.

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Figure 10: Iteration 3 (CAD Model)

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Figure 11: Video Demonstration of CAD Assembly

We then developed our first working protoype of the horse simulator. We 3D printed the links, horse, gears, and rack, and used metal pins to connect the joints of the linkage. We intend to later implement the electronic components to drive the mechanism, but we succeeded in our goal of designing and validating our 4-bar mechanism and perform our intended motion.

Draft BOM