mechanism motion linkage mechanism designer simulator

 http://www.roboanalyzer.com/mechanalyzer.html

 https://hackaday.com/2018/01/26/amazing-mechanical-linkages-and-the-software-to-design-them/

 https://blog.rectorsquid.com/linkage-mechanism-designer-and-simulator/

 Machines | Free Full-Text | Linkage and Cam Design with MechDev Based on Non-Uniform Rational B-Splines

https://www.mdpi.com/2075-1702/8/1/5