In the vast expanse of space, where satellites and debris orbit silently, a new breed of robots is being developed to tackle the challenges of on-orbit services. These space robots, equipped with sophisticated manipulators, are designed to perform tasks such as refueling, debris removal, and repairing malfunctioning satellites. The stakes are high, and the technology is cutting-edge, with significant implications for the energy sector and beyond.
At the forefront of this research is Qian Sun, a scientist from the School of Automation Science and Electrical Engineering at Beihang University in Beijing. Sun and her team are delving into the complexities of planning and controlling space robots for on-orbit capture, a task fraught with dynamic challenges and environmental uncertainties.
One of the primary hurdles in path planning for space robots is the dynamic singularity that can occur when solving inverse kinematics in task-space. Unlike terrestrial robots, space robots must contend with the dynamic coupling between the base spacecraft and the manipulator. “The motion of the base spacecraft can be influenced by the manipulator’s movements,” explains Sun, highlighting the need for sophisticated trajectory planning that minimizes base disturbances.
The path to successful on-orbit capture is littered with obstacles, both literal and figurative. Space robots must navigate around debris, adhere to input and velocity constraints, and, in the case of dual-arm robots, coordinate the movements of two manipulators. “Coordination between two arms is crucial for some complicated space missions,” notes Sun, underscoring the need for advanced control strategies.
Once the trajectory is planned, the next challenge is tracking control. The high nonlinearity, multidimensionality, and strong coupling of the space robot system make this a formidable task. The end-effector must quickly reach the capture points, all while ensuring steady-state and transient performance. “The controller design should guarantee both steady-state and transient performance, such as slight overshoot, small steady-state error, and short transient time,” Sun emphasizes.
The space environment adds another layer of complexity. Unknown external disturbances and parametric uncertainties can negatively affect control accuracy, requiring robust compensation mechanisms. “The proposed control strategy should ensure overall system stability, fast convergence, and strong robustness against disturbances and uncertainties,” Sun states, outlining the rigorous standards that must be met.
Before these robots can be deployed, comprehensive ground-based verifications are essential. Simulating the microgravity environment of space is crucial for accurately reflecting real space motions. This is where the application of intelligent methods in multiobjective optimization and disturbance rejection control comes into play, leveraging the rapid development of artificial intelligence.
The research, published in the Journal of Engineering Science, provides an overview of recent advancements in path planning and tracking control, focusing on the dynamic characteristics of space robots and the complexities of the space environment. It also discusses relevant ground-based verification technologies and highlights the existing limitations and potential future developments in the field.
The implications for the energy sector are profound. As space becomes increasingly congested with satellites and debris, the ability to perform on-orbit services will be crucial for maintaining operational efficiency and reducing the risk of collisions. Space robots could revolutionize satellite maintenance, extending their operational lifespans and reducing the need for costly replacements.
Moreover, the technology developed for space robots could have terrestrial applications, particularly in industries requiring precise manipulation and control in challenging environments. The energy sector, with its need for reliable and efficient operations, stands to benefit significantly from these advancements.
As we look to the future, the work of Qian Sun and her team at Beihang University offers a glimpse into the possibilities that lie ahead. The development of space robots for on-orbit capture is not just about advancing space technology; it’s about pushing the boundaries of what’s possible in robotics and control systems. The energy sector, and indeed many others, will be watching closely as these technologies evolve, eager to harness their potential for innovation and growth.
