Modular robot manipulators have many advantages over conventional integrated robot manipulators, including flexibility, re-configurability, versatility, and low-cost with massive production. However, the lack of control precision has been a long standing drawback in MRM applications until now. In this paper, a VDC-based control and communication system using embedded FPGA (field programmable gate array) logic devices is outlined. This solution is able to push the control precision to a new level without needing joint torque measurements. A test case on a three-module robot using harmonic drives demonstrated that the ratio of the maximum position tracking error to the maximum velocity reached 0.00012 (s).

This paper provides an overview of the Canadian Space Agency’s recent developments in space robotics and their relations to the CSA Exploration Program’s most recent mission roadmaps. The roadmap is structured by destination ranging from LEO missions focusing on the usage of the International Space Station, to Lunar, Near-Earth Objects and Mars missions. For each activity thrust, the paper describes recent and on-going robotics developments of the Canadian Space Agency. These activities span the entire space from concept studies, prototype development, field-trials, all the way to space missions and commercialization.

CSA (Canadian Space Agency) is currently developing and conducting a series of experiments dubbed Avatar to investigate different command and control schemes allowing operators to interact with robots in space or on other planets. The objective of the Avatar experiments is to develop and test concepts in support of future space exploration missions. Although some of the concepts can be (and have been!) tested on Earth by simulating space-relevant communication links, the benefits of conducting them from the ISS are numerous. First, the usage of an intermittent amateur radio link has raised several issues regarding the robustness of the software: it is impossible to cheat when the communication link really goes down. It has also allowed the team to develop unique operational expertise. One final advantage not to be neglected is the fact that these experiments will have provided flight heritage to the command and control concepts described in this article and to the software that was used to implement them. Such heritage is precious in the traditionally conservative space community.

The international exploration initiatives currently being defined by most space agencies place a strong emphasis on robotic missions: either as support of human missions or as precursor to astronaut flights. One scenario being considered is to have a system on a planetary body, such as Mars or the Moon, operated by a human in a spacecraft orbiting around it. Such robotic system should have various levels of autonomy for better efficiency. In that context, the Canadian Space Agency (CSA) has initiated the Avatar project consisting in a series of missions used to validate and increase the level of maturity of its autonomous robotic and software technologies. This paper presents the first planned mission, Avatar RESCUE, where a robotic test bed located at the CSA headquarters will be operated from the International Space Station using a low bandwidth amateur radio link.

One important area for application of space robotics is autonomous on-orbit servicing of failed or failing spacecraft. In this work, we describe laboratory experiments that verify the feasibility of autonomous capture of a slowly spinning non-cooperative satellite by a manipulator. The developed algorithms have been implemented and tested with the Canadian Space Agency's Automation and Robotics Test-bed, a two-arm, seven degree-of-freedom (dof) each, manipulator system. In the first phase of this work, a redundancy resolution scheme was implemented to maximize the robots' manipulability and increase their functional workspace. In the second phase, an online vision-based trajectory generation algorithm generating a velocity command to safely approach the target satellite and match its motion was developed. An overview of this work and the important results are presented.

The interest in new demonstration missions of space servicing is decidedly rising in this beginning of the twenty-first century, as attested by several well-known projects like the Orbital Express, TECSAS, CX-OLEV and others. Such missions require a thorough knowledge of the mechanical behaviour of spacecrafts during docking or berthing. In order to adequately study the dynamics involved, a number of docking emulation test-beds have been elaborated worldwide and tested for their efficiency in providing realistic results, thereby preventing an eventual failure of the docking process. The Canadian Space Agency is developing such a test-bed for spacecraft docking emulation by using hardware-in-the-loop simulation. This paper describes this test-bed and presents the verification procedure used to verify the functionality of this type of simulation.

´ eal (QC), Canada, H3C 3A4ABSTRACTMany demonstration missions such as Orbital Ex-press, DART, XSS-11, TECSAS, and the possiblerobotic servicing/decomissioning of Hubble have re-cently been planned. A common, important elementto many of these missions is the necessity of me-chanically interfacing the spacecrafts involved. TheCanadian Space Agency targets the utilization of ahardware-in-the-loop simulation (HLS) to emulatethesatellite-dockingprocedure. Thispaperdescribesthe spacecraft models implemented in the simulator,the orbital mechanics module, as well as the attitudeandorbitcontrolsystems. Thesimulatorcanbeusedin one of the pure simulation or the HLS modes. Inthe former, a contact-dynamics model computes theforces and moments involved in the docking, whereasthe actual docking hardware is used in the latter toobtain the contact forces and moments.1. INTRODUCTIONOn-orbit servicing has recently received renewed at-tention with planned demonstration missions suchas Orbital Express

As a partner in the International Space Station (ISS), Canada is responsible for the verification of all tasks involving Dextre, also known as the Special Purpose Dextrous Manipulator (SPDM). Those verifications cannot be performed using only software simulators since the accuracy of current contact dynamic models are yet to be confirmed. Instead, a solution involving hardware-in-the-loop simulation was retained. With this option, the space hardware is simulated while the contact dynamics is emulated using a rigid robot performing the tasks. Using this approach, the Canadian Space Agency developed the SPDM Task and Verification Facility (STVF). The approach suggested to validate STVF is based on first building confidence by comparing experimental results with pure simulation results for cases easy to model. Then, the complexity of the experimentations is increased. Preliminary test results presented in this paper show that STVF is performing well.

In this paper, we describe the development of vision-based algorithms for determining the motion of a moving object and generating trajectory for a robotic manipulator to intercept the object. The ultimate goal of this work is to develop autonomous algorithms for robotic grasping of objects in space. This problem arises in several applications, including on-orbit servicing of satellites and removal of space debris. The proposed methods have been implemented and tested in simulation and are currently being implemented on an experimental facility. The facility is based on a novel concept for experimental evaluation of robotic capture of free-floating objects, in particular, to use a small helium airship to emulate a free-floating object. The paper presents a brief overview of the main components of the facility, describes the vision-based motion estimation, trajectory generation and redundancy resolution algorithms implemented thus far and presents simulation results demonstrating the performance of these algorithms.

Satellite servicing represents a considerable challenge for space engineering. Each mission requires important investments in terms of human and financial resources, and thus several space agencies are trying to find an ecient way to restore satellites by unmanned missions, using autonomous repair spacecrafts. However, there are specific complications related to this type of operation, one of them being the critical nature of the docking stage that, if not done in strict accordance to the set parameters of velocity and angle of approach, can jeopardize the entire mission, hence the extensive research that is presently being conducted in the field of contact dynamics. The focus of this research is to find alternatives to the methods that are currently in use for dynamic estimates, as they do not deliver reliable results particularly in complex situations. This behavior is mainly due to the fact that dynamic results change drastically with each variation of the calculation parameters. In an eort to solve this problem, researchers have developed experimental setups that can help generate more realistic re- sults.

Many demonstration missions such as Orbital Ex- press, DART, XSS-11, TECSAS, and the possible robotic servicing/decomissioning of Hubble have re- cently been planned. A common, important element to many of these missions is the necessity of me- chanically interfacing the spacecrafts involved. The Canadian Space Agency targets the utilization of a hardware-in-the-loop simulation (HLS) to emulate the satellite-docking procedure. This paper describes the spacecraft models implemented in the simulator, the orbital mechanics module, as well as the attitude and orbit control systems. The simulator can be used in one of the pure simulation or the HLS modes. In the former, a contact-dynamics model computes the forces and moments involved in the docking, whereas the actual docking hardware is used in the latter to obtain the contact forces and moments.

Over the last two decades, the international space community has been discussing the merits of on-orbit servicing (OOS) of satellites. Because of the high cost and risk associated with the establishment of an on-orbit servicing infrastructure, OOS is not yet commonplace. The streamlining of operations is of vital importance to the economic viability of OOS. One of the technologies that will undoubtedly contribute greatly to the reduction of operations costs is on-board autonomy. The Canadian Space Agency is participating to a DLR-led mission called TECSAS whose objective is to demonstrate technologies that are key to the viability of OOS. A portion of the CSA’s contribution to TECSAS is the on-orbit demonstration of autonomous OOS operations. The technologies to be demonstrated by CSA during TECSAS include the Cortex toolbox for on-board autonomy software and the re-configurable ground control station developed under the Autonomous Robotics and Ground Operations (ARGO) framework.

Analyses the performance and stability of a force/moment accommodation (FMA) loop closed around a joint rate controller. A synthesis methodology is given to select the gains of the accommodation controller. The bandwidth and coupling limitations of the FMA control architecture are discussed. It is shown that the closed-loop FMA exhibits natural decoupling when FMA acts on the "transpose Jacobian rate" controller. The theoretical developments in the paper are supported by simulation and experimental results.

Docking an in-orbit satellite by another satellite is a challenging task, especially when the target satellite is not co-operative or not originally designed for docking operation. This paper discusses docking operation and proposes an attitude control method capable of assisting docking operation. Simulation study has demonstrated that the method can promisingly assist soft docking and therefore reduces the requirements for docking interface design.