SAM: cable-Suspended Aerial Manipulator for Work at Heights

Aerial Manipulation: What is it and Why?

Aerial manipulation involves using a robotic manipulator, such as a robot arm, to interact with and manipulate objects while operating at high altitudes.

A significant advantage of using an aerial manipulator is its ability to efficiently access areas that are otherwise difficult or impossible for traditional robots or human workers to reach. This advantage, combined with the benefit of being able to operate under dangerous conditions, makes aerial manipulators an excellent option for tasks such as inspection and maintenance at heights. Another advantage of utilizing aerial manipulators is the potential for reducing operational costs since working at heights requires a considerable amount of setup and preparation.

Developing a system that combines the capabilities of a robotic manipulator with the agility of an unmanned aerial vehicle (UAV) is a complex task. However, when executed correctly, this integration can revolutionize various industries by providing safer and more efficient solutions for performing tasks in challenging environments.

Revolutionizing Aerial Robotics: Introducing the cable-Suspended Aerial Manipulator (SAM)

Traditional aerial manipulators typically involve a flying system equipped with a robotic arm for interaction. While effective, these systems come with limitations, particularly in terms of collision risks and payload constraints.

The cable-Suspended Aerial Manipulator (SAM) offers a promising alternative. Instead of attaching a robotic manipulator directly to an aerial carrier (e.g., a crane or a helicopter), it is mounted to an active platform, with 8 propulsion units. The entire system is suspended by a cable from the aerial carrier. The role of the aerial carrier is to deliver and position SAM near the operation area. Then, SAM can carry out the task independently. This setup has several benefits, some of which are discussed below.

Enhanced Safety of Aerial Manipulation by Utilizing SAM

The core concept of SAM lies in the increased safety obtained through suspending SAM from the aerial carrier. Suppose that the carrier is a helicopter. Having the helicopter too close to an object is risky as the large rotor blades need to be at a safe distance from obstacles. In addition, having the carrier do the lifting allows SAM to have greater flexibility and focus on control and maneuverability, particularly during turbulence, which adds to the safety of the overall platform.

As a result, suspending the manipulator and the active platform from an aerial carrier can provide greater safety, control, and performance.

Innovative Actuation Systems

SAMs boast two primary actuation systems: winches and propulsion units.
The winches are responsible for continuously adjusting the length of the cables such that the Center of Mass (CoM) of the platform is maintained at an appropriate location while the robot arm is operating. This eliminates the need for the propulsion units to consume excessive energy to correct for CoM.

The propulsion units are used to handle the disturbances caused by the operation of the robot arms and stabilize the platform.

Thus, these systems work in tandem to ensure precise control and  maneuverability, even in challenging conditions.

Versatility and Universality of SAM

One of the key strengths of SAM is its versatility. That is, the platform can be adapted to various aerial carriers, including UAVs, manned aerial vehicles, or cranes, making it suitable for a wide range of applications. Examples of applications include wind turbine inspections, pipeline maintenance, and bridge repairs.

Effective Control Strategies

Disturbances are a serious issue when it comes to aerial manipulation. For example, disturbances from winds and the motion of the arm during operations can cause the system to become unstable. Thus, to maximize the performance of SAM, sophisticated control strategies, such as hierarchical whole-body control, have been developed.

These control strategies focus on damping oscillations, coordinating the robotic arm and winch dynamics, and ensuring stable operation in diverse environmental conditions. Through extensive simulations and experimental studies, the effectiveness and robustness of these control strategies have been validated.