Surface Operation Requirements for the ExoMars Rover Vehicle Instrument Deployment Arm (IDA)

A preliminary baseline design for the ExoMars IDA is the Beagle 2 (B2) arm, and the AU study has made extensive use of the B2 Development Model (DM) arm [Barnes-02, Barnes-03] which was part of the B2 Ground Test Model (GTM) situated at the Lander Operations Control Centre (LOCC), National Space Centre (NSC), Leicester UK. A test rig has been built that emulates the base and front sections of the ExoMars rover vehicle, and this has been raised to the proposed rover base height above nominal ground level. The B2 DM arm has been mounted on this rig, and electronics built to provide the necessary motor drive interface and low level joint motor speed control. The electronics also provides an interface to computing hardware for arm control input and joint angular feedback purposes. The entire test rig with B2 DM arm, electronics and computing is situated within the AU Planetary Analogue Terrain Laboratory (PATLab). As well as Mars Soil Simulant-D and target rocks, the PATLab has a twelve camera Vicon motion tracking system which has been used to provide arm positional and angular ground truth measurements throughout the IDA study. The study commenced with a repeat of the B2 DM arm positional repeatability and accuracy measurements originally conducted over 5 years ago. During the B2 mission the arm was to be moved joint-by-joint and employed a bang-bang [Sonneborn-65] joint motor control method, i.e. there was no simultaneous multiple joint motion, and no joint motor speed control. Given the demands of the future ExoMars mission, more advanced arm control methods will be required, and the AU study has involved the design, implementation and testing of a new joint-interpolated-motion algorithm which allows straight line manipulator control [Taylor-79]. A similar approach has been adopted for the two NASA Mars Exploration Rovers [Baumgartner-05]. Our work has culminated in the porting and demonstration of our autonomous arm placement control methods using the B2 DM arm and IDA test rig. This paper describes the work that we have undertaken for our Phase B1 IDA operation requirements study. Our results are presented together with a comprehensive list of recommendations that must be adhered to in order to achieve the proposed ExoMars IDA surface operation requirements.