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17.2 Project Prototype

17.2 Project Prototype

Iteration Documentation

From our original design presented in Figure 2.1 below, we created a first iteration of our final design, whose top and side views can be seen in Figure 2.2 below. The first iteration used a central motor to power the four-bar-controlled vertical movement and a second, offset motor to power the scissor motion and therefore direction. In our second iteration of the final design (see Figure 2.3 for top and side views), we offset both motors in an effort to stabilize the motors by mounting them flat against our base. To reduce weight, we shortened the crank length from about 5 cm in the first iteration to 2.5 cm in the second iteration. This allowed us to shorten the length of all links in the four-bar system. Please see the discussion below for more information on four-bar iterations. For procurement purposes, we decided to move from using motor drivers for each arm in the first iteration to using relays in the second. Finally, in our second iteration, we added a second base for stability and to provide the pulleys with two points of contact. Please see section 17.5 Final Demonstration for final iteration.

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Figure 2.1. Preliminary design.
Figure 2.2. 1st iteration of final design.
Figure 2.3. 2nd iteration of final design.

For our four-bar mechanism, we went through a couple iterations to ensure straight line motion for at least half of the crank rotation cycle. We are using a Hoeken linkage for this motion. The crank has length a, the coupler is 2.5a+2.5a, and the rocker is 2.5a. These proportions are chosen to produce an approximate straight-line path for a point on the coupler. Our first iteration of this mechanism (see Figure 2.4) was unsuccessful in achieving the desired path. With some changes made to the link lengths, however, we were successful in designing a Hoeken linkage that will produce linear motion for over half the cycle (see Figure 2.5 for second iteration). Our physical prototype of this four-bar linkage system is shown in Figure 2.6 below, which includes images of the mechanism at both the beginning and end of the linear motion phase.

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Figure 2.4. GIF of 1st iteration of four-bar mechanism design.
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Figure 2.5. GIF of 2nd iteration of four-bar mechanism design.
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B502FB0F-6B98-48F9-B3BB-6037186E1923_1_102_a-20250410-161914.jpeg

Figure 2.6. Prototype of four-bar mechanism design.

Draft BOM

Already have:

  • Arduino Uno

  • (Quantity: 2) Greartisan 10RPM 10kg*cm motor (ZGB37RG314i)

  • (Quantity: 3) L298N motor driver

  • Small breadboard

  • (Quantity: 5) Bearings

  • 12V DC power supply

  • Coupling

Need to purchase:

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