Chebyshev's Straight line Mechanism & Robert's Straight Line Mechanism

In continuance to the last article, which gave introduction about some special mechanisms and briefly explained Watt's straight line mechanism, in this article few more approximate straight line mechanisms will be discussed. These are different configurations of four bar linkages and yield reasonable approximations to linear motion. The Chebyshev approximate straight line mechanism is also a four bar linkage mechanism that is both historically important and also of practical importance. Robert's approximate straight line mechanism is a symmetrical four bar linkage.