Robot hands can now mimic human tactile dexterity

The Shadow Dexterous Hand equipped with human skills, designed to operate in human environments and use tools made for humans

From farming to pharma, the Shadow Dexterous Hand is revolutionising the way that robots are used across a number of sectors. Whether used as a remote controlled tele-operated tool, or mounted on a range of robot arms as part of a wider system, the Hand takes a totally new approach to robotic manipulation. By closely mimicking the movements and dexterity of the human hand, it is able to carry out a number of tasks that have been beyond the capability of robots until now.

Founded in London in 1987 by a group of robot enthusiasts, the Shadow Robot Company (the company behind the Hand) has since evolved into one of the UK's most established robotics firms, and one of the leaders in dexterous robotic manipulation technologies, or ‘hands for robots'

The company's founders spent years thinking of ways in which robots could be applied to solving real world problems, how they could be equipped with human skills, operate in human environments, and use tools designed for humans. This led them to consider manipulative robotic hands, developing this further once they realised that, if a robot took the form of a human hand, it would be easier for operators to understand how to control it remotely via teleoperation.

Since then, the company has gone on to produce the world's most advanced anthropomorphic hand, developed a 'smart grasping hand' for use in the manufacturing industry, and work with organisations including Qualcomm, GDK and NASA.

Tactile sensitivity

When developing the Shadow Dexterous Hand, the top priority was to approximate the movement of the human hand's individual bones, joints and tendons. To achieve the required level of flexibility, the company designed 20 actuated degrees of freedom, and four additional under-actuated movements across 24 separate joints, each with a range of movement similar to that of the human hand, including the thumb and the flex of the palm for the little finger.

An impressive feat of miniaturisation means that a device the size of the human hand contains a total of 129 sensors. A combination of absolute position sensing for each joint, force sensing for each actuator, temperature, motor current and voltage sensing, and ultra-sensitive touch sensors on each fingertip together deliver the Hand's tactile sensitivity.

Creating each of these highly sensitive components on the Hand's fingers and fingertips required bespoke precision manufacturing, a service provided by digital manufacturer Protolabs.

Highly specific geometries

Protolabs has been producing high-quality parts for the Shadow Robot Company for a number of years, using rapid manufacturing technology to meet the fast turnaround of components demanded by the ever-evolving robotics industry.

Given the highly specific geometries required, it was decided early on in the development process that injection moulding would be the manufacturing process most appropriate for producing the plastic parts that comprise the Hand's fingers, as it delivered the structure and surface finish they required.

The technique delivers repeatable, reliable and consistent results throughout the manufacturing process, allowing the company to produce the components time and time again as required, without risking any drop in quality.

In addition to these, aluminium parts for the pressure sensor tiles, key components in making the Hand's fingertips so highly sensitive, were manufactured using Protolabs' CNC machining technology, a process in which computers are used to control high-speed milling and turning tools.

Marriage of innovation and manufacturing technology

A number of different industries have been employing robots for decades, with robotic hands a common feature in heavy manufacturing plants in particular. Replicating the strength, sensitivity and range of movement of the human hand, however, has long been a goal for the Shadow Robot Company.

Now though, following years of research and development, and by employing the most advanced manufacturing techniques, the company has created a robotic hand that can be relied upon to manage the cable tethering an astronaut to his spacecraft, that is sensitive enough to handle an egg without breaking its shell, and is even flexible enough to stir up a crab bisque.

The Shadow Dexterous Hand is the perfect marriage of innovation and manufacturing technology; with applications ranging from performing remote surgery to picking fruit, and from carrying out previously inaccessible repairs to safely defusing explosives, the potential of the Hand spans a wide range of applications.>

Stephen Dyson is head of industry 4.0 at Protolabs