MATLAB Simulation and Calculations

Given the link lengths that we determined would yield a sufficient mechanical advantage for our device, we then used MATLAB to calculate a rough estimate of the mechanical advantage that our device would experience while the links moved through their full ranges of motion. Our process was as follows:

• Create MATLAB functions that performed position and velocity analyses for fourbar linkages given the link lengths, the position of the input link, and the angular velocity of the input link
• Create and run a MATLAB script that called these functions and created plots of mechanical advantage versus position of input link.
  
  

The calculation of the mechanical advantage was performed using the following assumptions:

• r_in was set equal to the estimated distance between the point where most people would grab the input lever and the grounded point on that lever (about 9.125 in)
• r_out was set equal to the distance between the grounded point on the link with the slot cut into it and the midpoint of that slot, which serves as a conservative estimate for the point of application of output force (about 1.275 in)
• omega_in was set equal to the angular velocity of the input lever
• omega_out was set equal to the angular velocity of the output link of the outer fourbar mechanism

Results

Figure 1: Mechanical Advantage for Full Range of Possible Angles of Input Link                       Figure 2: Mechanical Advantage from Lower Position Limit to Just Before Toggle Point

Figure 3: Mechanical Advantage from Just After Toggle Point to Upper Position Limit                         Figure 4: Mechanical Advantage for Small Range that Includes Toggle Point

MATLAB CODE

• Position Analysis

• Velocity Analysis

• Mechanical Advantage Calculation