09.2 - Project Analysis and Prototype

Kinematic Analysis

Analysis of Casting Mechanism

Ideal Motion Profiles:

Output Link

The output link for the casting mechanism ideally would start in the back position and once in motion will whip forward to bring the link to the final casting position.

Displacement of Output 

Linear Velocity of Output

Linear Acceleration of Output 

Input Link

The input link for the casting mechanism is connected to the ground link that moves with the output link of the positional adjustment mechanism to move the output link of the casting mechanism.

Displacement of Input 

Linear Velocity of Input 

Linear Acceleration of Input 

Mobility Calculation (Grubler's Equation):

Gruebler's Equation is vital for calculating the mobility of robotic mechanisms. It helps determine a mechanism's degree of freedom by considering the number of links, joints, and their respective degrees of freedom. Below is the calculation to determine the mobility of our casting mechanism design.

Mechanical Advantage of Output/Input

The mechanical advantage of the output was determined using the kinematic velocity data obtained from analysis. By assuming power is preserved throughout the mechanism, we can plot the input velocity divided by the output velocity at each point in time to give mechanical advantage of the mechanism. 

Connector Rectangle (3D)

In our prototype, we were able to accomplish 3D motion with the mechanism. To do this we created a piece called the Connector Rectangle, shown below, that was attached to the positional adjustment mechanism ground link and the casting mechanism link 3. The casting mechanism link 3 had a rectangular slot at a 45° to be able to attached to the positional adjustment mechanism ground link perpendicularly.

Animation showing linkage operation in the full range

Analysis of Positional Adjustment Mechanism

Ideal Motion of Link 1:

Displacement and linear velocity for one full rotation of link 1:

Input - 15 rpms

Physical Prototype

For this submission, we needed to build a functional prototype that shows working proof of concept by displaying the manual powered full range of motion of the mechanisms for the autonomous fishing rod.  As seen through the analysis and iterations of the fishing rod, we were able to build a prototype that displays the casting in 3 planes of motion. With these upcoming weeks we will be fine tuning the design for the final project submission. 

Iteration Documentation

Casting Mechanism Design 

Iterations between the original design of the casting mechanism include the changing of link 3 to have a slot for the connector rectangle, which connects the casting and positional adjustment mechanisms. When laser cutting the parts, we had iterations for the links due difficulty in assembly because of lengths and diameters of holes.

Output Link

The output link initially had a slider but after testing and analysis, it was concluded that a bearing connection was more effective. 

Ground Link 

The slot for the slider in the ground link had to be adjusted to connect to the position adjustment mechanism. The slot had to be wide enough to fit the output link of the position adjustment mechanism and the connector rectangle. 

Link 3 

Link 3 also had to be adjusted to connect to the position adjustment mechanism. It stays at a fixed angle during motion, so the angle was determined using the geometry of the casting mechanism and a slot was added at the corresponding angle for the connector rectangle. 

Connector Rectangle

This rectangle was used to connect the position adjustment mechanism (XY plane) with the casting mechanism (ZY plane) and maintain the angle of link 3. 

Final Casting Mechanism 

The final design shows the results of iteration. The ground link and link 3 were adjusted to connect to the position adjustment mechanism and the design iteration of link 4 (output link) with a bearing was chosen for the final prototype. 

Positional Adjustment Mechanism

Original design, using a linear actuator as input:

First iteration of rotational input:

Final CAD of Prototype (Connection between our two mechanisms not pictured, connector rectangle):

Bill of Materials

Most of the parts needed for this project are provided by the RMD class or can be purchased at TIW. There are two items that will need to purchased for the fishing rod, the fishing wire and a linear actuator. In our initial brainstorm, we were considering using the linear actuator to translate between the two planes of motion for the design. However, during the prototype phase, we were trying to find a solution before purchasing the linear actuator. 

Laser Cut Components:

• Positional Adjustment Mechanism (slider-crank)
• Casting Mechanism (5 links)
• Connector Rectangle
• Spacers
• Bases

Electronic Components:

• Linear Actuator
• 360 Degree Servo
• Wires
• Arduino
• Power Supply
• Button

Stock Components:

• Fishing Wire
• 6mm Bearings 
• 6mm Stainless Steel Shaft
• Nuts
• Bolts