I-Introduction and Background

I have always been fascinated by walking robots, both bipedal and quadruped systems. However, frequently these robots feature a complex grouping of actuators and sensors to precisely control the position and speed of the overall machine. Alternatively, mechanisms can be designed and used to overcome other system restrictions, for example a limitation to one actuator on a crank. These mechanisms strive to convert the rotational input at a crank or gear to an output trajectory at the "foot" of the linkage that resembles the path shown below with some combination of links, gears, cams, or other mechanical features. 

With this trajectory, the "foot" of the leg linkage is placed firmly on the ground, shifts the body of the robot or "ground" forward, lifts smoothly, and then repeats. This simple path is desired for its stability, and with proper timing between steps and enough legs, a robot could stay relatively level. While this may be the ideal path, the perfect trajectory for any robot will also depend on the weight distribution, the surface it is built for, and other factors. However, the focus here was to try and get as close as possible to the desired path above with the linkage. 

Klann Linkage

Strider Simple Four-Bar Linkage

Jansen Walking Linkage

Though a linkage with multiple actuators provides an opportunity for greater control and movement on a variety of surfaces, this simplified walking robot can have several applications as well. Overall there are many papers and linkages capable of accomplishing this task—some shown below—and move robots without the conventional motor and wheel setup. Thus, my goal was to research, design, and build a much more simple walking linkage that could use one input crank to achieve the desired "walking" position trajectory shown above.