Extended virtual passive dynamic walking and virtual passivity-mimicking control laws

In our previous works (2000), we have proposed "virtual passive dynamic walking" utilizing modified gravity condition with virtual gravity field. The virtual passive walking motion critically depends on the physical parameters and the steady walking pattern is not easily obtained without suitable physical parameters. In this paper we propose a more generalized method of virtual passive walk and a virtual passivity mimicking control law. With the effect of the control laws, we can generate the steady walking pattern even if the physical parameters are not suitable. We call the walking pattern generated by the control methods as "extended virtual passive dynamic walking". The validity of the proposed method is examined by numerical simulations and tested by a prototype experimental machine.