Linkage synthesis is designing a linkage to meet a desired output. Since most linkages are capable of complex motion, this has been a daunting task except for specific linkages with predictable motion. In this article we will look at various types of linkage synthesis.
Before getting to far, we need to define the term "precision point".
Precision Point A specified x,y value on a path that a point on the linkage must pass through.
Types of Linkage Synthesis
There are three basic types of linkage synthesis that can be performed. Each has a different goal or desired output.
A path is specified that a point on a link must follow. How the linkage accomplishes this path is not of concern. For example, a four bar linkage shown below has a point on link 3 that passes through each precision point as link 2 rotates.
The purpose of function synthesis is to design a linkage that acts as a function generator. For a given input link angle, the output link angle must be at a specified angle.
Assuming link 2 is the driver, we can create a function generator with either link 3 or link 4. As link 2 is at a given input angle, we have an output angle of link 3 or 4 depending on which link is of interest.
With motion synthesis a path is specified that a point on a link must follow, and the angle of that link at each precision point is also specified. For example, if the point is on link 3, we want to synthesize a linkage where the point passes through each precision point and when it passes through a given precision point, link 3 is at a specified angle.
Timed vs. Untimed Synthesis
In addition to the three types of synthesis discussed earlier, there can be timed and untimed synthesis. With timed synthesis, the driving link angle must be at a specific angle for a given precision point. Untimed synthesis is not concerned about driver angle and it can be any value.
For function synthesis, it is always timed since we are generating a function where driver angle is the input and the driven link angle is the output.