## Wing Mechanisms

Repurposing Jansen’s Leg Mechanism:

Innovative mechanical flyers were designed by student teams in my Kinematic Synthesis class based on a repurposed version of Jansen’s leg mechanism. The artist Theo Jansen has inspired many of my students with his dramatic assemblies of leg mechanisms to form his Strandbeest wandering on a beach under the power of a sea breeze.

A generalization of Jansen’s leg has the hip and knee joints driven by separate four-bar function generators to provide a wide variety of foot trajectories. This generalized version of Jansen’s linkage can be adapted to form a wing mechanism that has a desired wing-tip trajectory.

This video shows the Geogebra model of a wing mechanism based on Jansen’s linkage, and three digital prototypes of mechanical flyers obtained by my students using this mechanism.

## Six-Legged Mechanical Walkers: Spring 2020 Highlights

The leg mechanisms of these six-legged walkers use two coordinated function generators to drive the hip and knee joints to achieve the desired foot trajectory. This differs from Jansen’s leg mechanism in the following ways: (i) separate cranks can be used to drive the hip and knee joints, rather than the same crank driving both joints; (ii) the drive of the hip joint need not be connected at the knee but can connect any where on the upper leg; and (iii) a true parallelogram is used to connect the drive around the hip down to the knee, whereas Jansen’s connection has one side slightly larger for both pairs (39.3, and 39.4 for one pair of sides, and 40.1 and 36.7 for the other pair). So these leg mechanisms can be viewed as generalizations of Jansen’s design.

Stable gait for these walkers can be achieved by coordinating three legs at a time to form a tripod gait. Please see this video showing walkers designed by my students to be a crocodile, rhinoceros, bug, legged container and the Star Wars All-Terrain Tactical Enforcer, known as AT-TE. These assemblies of six 10-bar linkages connected by a gear train of as many as 18 gears posed a challenge to SolidWorks motion analysis for my students. We will get better at this.

## Prototype Four-Legged Mechanical Walker

Kevin Chen and Arwa Tizani designed this four-legged mechanical walker using Curvature theory to identify a flat-sided coupler curve of a four-bar linkage. This curve was positioned to be the foot trajectory of the leg mechanism using a skew-pantograph.

Kevin collected the parts and assembled the walker. Here are his photos and video of its performance.

## Four-Legged Mechanical Walkers: Spring 2020 Highlights

The design of these four-legged walkers relies on Curvature theory to find a flat-sided coupler curve of a four-bar linkage to be used for the foot trajectory. This coupler curve is repositioned using a skew pantograph. The result is a six-bar leg mechanism.

Stable gait for these walkers can be achieved by adding side-to-side foot extensions to broaden the support polygon during walking.

Please see this video showing walkers designed by my students to be a rabbit, two dogs, a bear, a rhinoceros, a dinosaur, and a centaur, as well as a legged platform, a legged syringe and the Star Wars All-Terrain Attack Transport, known as AT-AT.

## Fall 2019 Mechanical Walker Prototypes

I was pleased to have an enthusiastic group of graduate students work with me on the design of four-legged walkers as the final project for MAE 245 Kinematic Synthesis. Each of the teams designed a four-bar linkage using Curvature Theory to obtain a coupler curve with a flat portion that could be used as the foot trajectories for the legs of the walker.

Then, they placed the coupler curve in position to form the feet of a walker by using a skew pantograph for the front legs and rectilinear six-bar linkages for the rear legs. I required this particular choice of the type of legs, simply because I was not sure which would work better.

This video shows the operation of their design prototypes. They all work as designed, though we have more work to do on their fabrication in order to improve performance.

## Halloween Display 2019

This video shows how the linkage systems moving spooky decorations designed by my six student teams were combined into a Halloween display.

The Halloween decorations designed by project teams 4, 5 and 6 can be seen in the video

## Halloween Design Project

Students in my MAE 245 Advanced Kinematic Synthesis class have designed Halloween decorations using a four-bar linkage by itself or in combination with a parallelogram or pantograph linkage. You can see the work of teams 1, 2 and 3 in the video.

## Leg Mechanism for a Mechanical Walker

This is an animation of the leg mechanism for a mechanical walker designed using function generators to drive the hip and knee joints. A second parallelogram linkage is used to construct a translating leg that allows placement of the foot trajectory where ever the designer chooses.

## Construction for Three-Position Synthesis of a Four-Bar Linkage

The graphical construction of a four-bar function generator that coordinates three input and three output angles is presented in the video below. It is possible to coordinate as many as five input-output angles, but this requires numerical calculations using software like our MechGen FG iOS application.