Robot Actuators: Enhancing the productivity by reaching the edge of the possible

Robot Actuators: Enhancing the productivity by reaching the edge of the possible

ARIA's Robot Dexterity programme

What is ARIA's Robot Dexterity programme?

Breakthroughs in AI are transforming robotic abilities, but the development of robot bodies has not kept pace with advances in computation. Robots cannot achieve the flexibility, speed, and precision of human manipulation, rendering them useless for many of the difficult or dangerous tasks where we need them most.

This programme's goal is to release the bottlenecks in robotic dexterity and create vastly more capable and useful machines. We're funding an array of cutting-edge research across sensing, actuation, co-design, and advanced simulation. This blog offers a summary of the actuator projects and how they are pushing the current state-of-the-art in robot dexterity and beyond.

Why are actuators important for robots?

'Actuators for robots' are equivalent to 'muscles for humans' - an actuator takes energy as the input and produces motion as the output. Actuators enable the robots to perform the tasks (grasping, manipulating, lifting, etc.) and also interact with the environment. The performance of the robots in terms of accuracy, precision, reliability, etc. is heavily dependent on the actuators that are embedded in the robot bodies.

What's the current state of the art?

There are different categories of actuators and the choice of actuator for a particular application depends on various parameters like power-density, reliability, durability, speed, cost, energy efficiency, precision, etc. The major actuation technologies used today are hydraulic, pneumatic and electric motors. These are all highly mature, dating back to the nineteenth and even eighteenth centuries. In robotics, actuators are usually electric motors, because they are clean, quiet, efficient and powerful and offer precise control over both speed and position. However, electric motors also have some key disadvantages. For one thing, they operate most efficiently at high speed and low torque. While this has been appropriate for many applications in industrial automation, robots often require high torques (to lift things) at low speeds (to work safely alongside humans). Electric motors therefore often require gearboxes to amplify torque and reduce speed. Gearboxes come with their own problems, like reflected inertia, lack of backdrivability and increased cost and weight. The potential offered by new materials, advanced designs, and sophisticated control methods remains largely untapped in actuator technology.

ARIA's Robot Dexterity programme is tackling the problem at several different levels, ranging from miniaturisation and removing the need for gearboxes to exploring new designs and different technologies. These projects aim to deliver a new generation of actuators-highly energy-efficient, intelligent, compact, and bio-inspired-which will enable robots to be more adaptable, efficient, and safer for interaction.

Actuator projects - ARIA's Robot Dexterity Programme

Sangtera - Microhydraulic actuator

Robotic systems currently use inductive servo motors with high gear ratio to achieve high torque, but inherent limitations on energy efficiency and torque density prevent further scale-down to deliver the performance and form factor that suit the needs of a robotic hand. Sangtera is developing the next generation robotic actuator, by improving the size and reliability of electrostatic actuators. Sangtera's actuators, powered by surface tension, offer torque densities hundreds of times greater than traditional options, making possible compact gearless designs. Whereas traditional inductive motors become less efficient the smaller they are made, Sangtera's high-torque actuators can be made compact with no loss of efficiency. Their goal for this project is to develop a powerful actuator small enough to fit into a robotic finger joint. This would enable a completely new design approach towards human-like dexterity: actuating finger joints directly rather than via tendons.

Stellar Advanced Concepts Ltd - Pneumatic actuator

The project's mission is to design and prototype an adaptive pneumatic artificial muscle (PAM) for next-generation robotic systems. Air muscles offer numerous benefits for achieving dexterous robots that are safer for interaction with humans and delicate objects. The compressibility of air in pneumatic actuators makes them a good fit for safe interactions with humans and delicate objects. However, the soft actuator characteristics of current pneumatic muscles does not allow precision position and velocity control at low speeds and varying loads. Stellar AC will develop a novel stacked arrangement of PAMs that offers high-strength precision grip and position, and force feedback, beyond contemporary soft robotic muscles. This unique approach uses contact forces imparted along overbraided sleeves to allow precise control through internal pressure variations. The concept can be extended beyond dextrous manipulators to precise soft-robotic control of mechanical linkages in bio-inspired systems.

Artimus Robotics - Electrohydraulic actuator

Artimus Robotics has developed a fundamentally new class of high-performance soft actuators known as Hydraulically Amplified Soft Electrostatic (HASEL) actuators that use electrostatic forces to pump hydraulic fluids, driving shape change in a soft hydraulic structure. HASELs provide transmission-free linear actuation to enable adaptable, cost-effective, silent, energy-efficient actuation with muscle-like performance. Artimus is already supplying HASELs for underwater robotics, haptic human-machine interfaces, and industrial automation. However, current HASELs need further development to be integrated into human-scale robotic systems. The team's goal in this project is to develop new materials and architectures for HASELs to enable cost-effective dexterous manipulators with high strength, speed, and adaptability for a wide range of markets.

Pliantics - Dielectric elastomeric actuator

Dielectric elastomer actuators (DEAs) are soft actuators with an elastomeric membrane sandwiched between two stretchable electrodes. Application of voltage increases the pressure, stretching the membrane between the electrodes, and the actuator retracts to the original shape upon removing the voltage, demonstrating muscle-like performance. DEAs are popular for their lightweight, high efficiency, silent operation and fast response times. The key disadvantages are high operating voltages, reliability of the material and fabrication challenges. Pliantics is proposing a novel, patent-pending geometry for DEA that can both reduce the operating voltages and ease the fabrication challenges thereby speeding up the production. The team's vision is for their actuators to enable stronger, safer, and more bio-aligned dexterous solutions in robotics, entertainment, automation, and healthcare.

Wavedrives Ltd - Electromagnetic actuator (with unique non-contact magnetic transmission)

Motivated by their experience building humanoid robots and the market demand, WaveDrives has developed and patented the Sarcomere Inspired Linear Actuation (SILA), a novel actuation technology with simple & scalable design. SILA can be operated at low voltages producing high power density and efficiency, low maintenance and near silent operation. Wavedrives is collaborating with aerospace and bionic prosthetics industries to develop advanced SILA actuators, whose technology and manufacturing readiness is increasing rapidly. In this ARIA-funded project, the team will miniaturise the SILA technology, while maintaining its efficiency and power density - to provide the muscle-like actuation and motion control needed for dexterous robotic manipulators at human scale.

Elysium Robotics - Dielectric elastomeric microfibres actuator

The key building blocks of Elysium's actuator are their proprietary dielectric elastomer microfibres. When a voltage is applied the positive and negative charges in the microfibre attract each other, stretching the fibre, and when the voltage is removed the fibre shrinks, resembling the characteristics of human muscle. The unique proposition of Elysium's DEA microfibres is that they can be produced at industrial scale, and bundled together to make strong muscles, all while being lightweight, energy-efficient, and cost-effective. Elysium is aiming to develop full-scale high-performance synthetic muscles that mirror human muscles in strength, speed, and agility. The approach is powered by Elysium's unique fibre manufacturing capabilities paired with their focus on material refinement in this project.

Createc - ElectroMagnetic actuator (resembling biological muscle attributes)

Createc have been using robot arms for robot manipulation for years, but are consistently held back by the limitations of gearboxes in the arms that have them, or in the low strength-to-weight ratio of arms that don't. Gearboxes bring in limitations like backlash (that impacts positional accuracy, repeatability, etc.), increased energy consumption when moving at speed, inertia amplification and loss of back drivability. Not having a gearbox means not being able to produce high torques, while suffering poor control and low efficiency at low speeds. In this project Createc will explore electromechanical actuator designs that more closely mimic the force/power characteristics of biological actuators, while retaining the established advantages of electric motors and gearboxes.

UPWARD (Northwestern University, Texas A&M, Shadow Robot Company) - Switched Clutch Actuation

The UPWARD team will develop a method, called Switched Clutch Actuation (SCA), for the control of advanced robotic hands. With SCA, power from a small number of velocity sources is distributed to the hand's joints via a network of electroadhesion-based clutches. SCA clutches are designed to be low inertia, low power, and very fast, allowing for smooth and efficient control. This approach promises dramatic reductions in the size and weight of robotic hands, increasing their utility for emerging applications such as humanoid robots.

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