Mobile robot apparatus and payload module for use with a mobile robot device

The device e.g. rover (100), has legs (104, 106, 108, 110) for movement of a chassis (102). A payload module is received and/or set by the chassis. The chassis for receiving and/or setting the payload module is moved by the legs. The chassis is moved related to an orthogonal three-dimensional coordinate system in six degrees of freedom. The chassis is positioned and/or aligned and the payload module is received and/or set by a linear motion of the chassis, where the chassis comprises a linear guide for retaining the payload module.