Figure 1. - A sketch of the configuration of Spider.
Résumé
La mise au point du manipulateur Spider (SMS-1) s'inscrit dans le cadre du programme à long terme de l'Agence spatiale italienne, amorcé en 1988 et qui vise à réaliser un robot volant autonome destiné aux interventions en orbite. Ce manipulateur constitue une première étape dans la mise au point de la technologie des interventions sur des charges utiles en orbite. Un premier modèle a été construit et soumis à des essais poussés. Une articulation et sa commande ont été expérimentées avec succès dans l'espace au cours de la mission Euromir 95. L'ensemble du manipulateur sera mis en oeuvre lors de la mission Jerico qui doit avoir lieu à bord de la station russe Mir en 1998.
Companies:
Tecnospazio (I),
Comau (I), Tecnomare (I), Telerobot (I), FIAR (I)
Scuola Superiore S. Anna (I).
Funding:
Italian Space Agency.
The development of the Spider Manipulation System (SMS) is part of the long term programme of the Italian Space Agency (ASI). The project began in 1988 to produce a free flying autonomous robot for in-orbit servicing. SMS-1 is a first step in the development of technology for in-orbit payload servicing (Figure 1). This paper gives an overview of the current status of the develop-ment of SMS-1 and the main features of the manipulator.
Figure 1. - A sketch of the configuration of Spider.
A flight model of the manipulator has been built (Figure 2) and this is now undergoing thorough thermal-vacuum and vibration testing. One joint and its controller have also been successfully operated in space during the Euromir '95 mission. Included in the development are an end effector fitted with sensors, a wrist force-torque sensor, a prototype controller based on an equivalent industrial device and a simplified operator interface implemented on commercially available work-station.
Figure 2. The SMS-1 manipulator arm.
SMS-1 is intended for servicing of payloads, under zero-gravity conditions, both inside of and external to the pressurised module of the International Space Station. Provided certain restrictions are respected, it will also operate under the normal gravity conditions found on Earth.
The design of the manipulator arm of SMS-1 is imitates the form of the human arm and features seven rotating joints. Joints 1 and 2 are in the shoulder subsystem, joints 3 and 7 are in the elbow subsystem and joints 4, 5 and 6 are in the wrist subsystem. Each joint of the arm is powered by an electromechanical actuator group composed of a motor, a gearbox, input and output shaft sensors and a brake.
Table 1 summarises the key performance parameters of SMS-1 when operating under zero-gravity conditions. This performance is met throughout the full the range of conditions found in the intended operating environment in space.
Table 1. Performance of SMS-1 under zero-gravity.
The SMS-1 arm, end effector and force-torque sensor have been designed to operate at temperatures as low as -40°C, and to withstand storage at
-60°C without suffering degradation.
To warm up the arm from the storage temperature at -60°C and bring it to the lowest operating temperature, internal heating caused by the action of electromechanical components of the arm such as the brake, is exploited thus avoiding the need for supplementary heaters.
The SMS-1 arm, end effector and force-torque sensor have been designed to operate in vacuum. Particular care has been paid to the selection of the material used for insulating electrical cables in order to avoid outgassing, a source of contamination which can adversely affect testing in vacuum and can degrade sensitive optical payloads in space.
To verify the capability of the SMS-1 arm, end effector and force-torque sensor to withstand typical launch loads, mechanical tests such as a resonance survey, and exposure to random and sinusoidal vibrations, are planned.
The SMS-1 manipulator is the result obtained at the end of the first phase of the technology development programme undertaken by ASI. SMS-1 has been conceived as a reference for planning future developments. This might include refinements to its design in respect of its mass, external dimensions, controllability and its performance in general.
Following the initial success of the Robotic Joint Control Experiment, carried out in the framework of the Euromir 95 Project, in which one actuator and its controller were tested on board the Russian space station Mir, the next important step will be to demonstrate the full capabilities of complete SMS-1 manipulator in-orbit as part of the Jerico mission, to be carried out on board Mir in 1988.
Preparing for the Future Vol. 7 No. 2