Nonlinear control system design for construction robots using state dependent parameter models.

This paper considers nonlinear Proportional-Integral-Plus (PIP) control of construction robots, with particular emphasis on two practical demonstrators: a 1/5th scale laboratory representation of an intelligent excavator; and a full scale (commercial) vibro-lance system used for ground improvement on a construction site. In both cases, the hydraulic actuators are modelled using a quasi-linear State Dependent Parameter (SDP) model structure, in which the parameters are functionally dependent on other variables in the system. The approach yields SDPPIP algorithms with improved performance in comparison to conventional linear control. In the case of the vibro-lance, the new approach has the potential to eliminate verticality errors that have previously lead to probe repair costs of over 8000 GBP on each occasion, whilst also reducing the time taken to complete a complete digging and packing cycle in comparison to a skilled human operator.