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.View Post
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.View Post
Our MechGen FG iOS application provides five position synthesis for four-bar linkages. A Demo of the iPad version is provided here. It is also available on the iPhone.View Post
The graphical construction of a four-bar linkage that coordinates two positions of an input crank with two positions of an output crank is presented in this video using Geogebra.
A linkage that coordinates the values of input and output angles is called a function generator. It is possible to design a four-bar linkage to coordinate as many as five input and output angles. However, this requires numerical calculations using software such as our MechGen FG iOS application.View Post
This video adds a skew pantograph to a four-bar linkage in order to reorient and change the size of the coupler curve. The result is a six-bar leg mechanism with a foot trajectory that is a scaled version of the original coupler curve.View Post
In this video, we start with a four-bar linkage and coupler curve and construct an additional crank with a floating link connected to the coupler point. This floating link becomes the leg of the Klann-style leg mechanism. Adjustment of the dimensions of the added links shapes the foot trajectory.View Post
This video starts with a four-bar linkage with a coupler curve that is to be used as the foot trajectory for a leg mechanism. It presents a Geogebra construction of two additional bars, one of which is connected to the coupler point and moves without rotating. This means the bar can be expanded into a leg that places the desired coupler curve where the designer specifies. This is described in Chapter 4 of Kinematic Synthesis of Mechanism.View Post
This video shows the construction of the cubic of stationary curvature. The intersection of the cubic of stationary curvature with the inflection circle, iw Ball’s point which is a coupler point that traces a locally straight line trajectory.
This video also shows how to vary the coupler point and the dimensions of the reference polygon for the four-bar linkage to vary the shape of the coupler curve.View Post
This tutorial constructs the inflection circle for a particular configuration of a four-bar linkage. This construction was recommended by my colleague Gordon Pennock because it is simpler than the one I provide in my book Kinematic Synthesis of Mechanisms.View Post
This tutorial shows how to use Geogebra to construct the canonical coordinate system for a particular configuration of a four-bar linkage.
It starts with a quadrilateral which is to be the configuration of the linkage at a particular instant. Then constructs the velocity pole and the instant center of the positions of the input and output cranks. Connecting these lines defines the collineation axis.
Bobillier’s theorem completes the construction by defining the tangent to the moving centrode.View Post