Gripper Technology – Future Challenges
Advances in robotics EOAT gripper technology mean that robots can now perform many of the tasks traditionally associated with the human hand. How do robotics engineers navigate the multitude of design considerations when developing gripper tech?
Not unlike the human race, a robot end effector’s ability to grip and handle objects has been central to the evolution of robotics and continues to drive the industry forwards.
New advances in gripper technology offer very tangible benefits for manufacturers in precision, performance and productivity. The EOAT gives a robot a specific functionality and can be changed to fit different applications or even be built to accommodate several processes at once.
Manufacturers can use end of arm tooling for picking, placing or packing objects and grippers can handle hazardous materials with minimal risk to employees. Additionally, robots can also replace human involvement with repetitive tasks which could lead to repetitive strain injuries.
There are a wide variety of grippers on the market to suit different applications. One of the most basic forms is a parallel motion two-jaw gripper, which is commonly used for lifting objects. However, there are a number of different designs including bellows grippers, O-ring grippers and needle grippers.
As well as their physical structure, grippers can vary in how they are powered.
There are four types of robotic grippers: vacuum grippers, pneumatic grippers, hydraulic grippers and servo-electric grippers. Manufacturers choose grippers based on which handling application is required and the type of material in use.
The vacuum gripper has been the accepted standard EOAT in industry because of its high level of flexibility. This type of robot gripper uses a rubber or polyurethane suction cup or a closed-cell foam rubber layer to pick up items.
The pneumatic gripper is very popular due to its compact size and weight. It can easily be incorporated into tight spaces, which can be advantageous in the manufacturing industry for handling purposes.
The hydraulic gripper provides the most power and durability and is often used for applications that require tremendous amounts of force. Hydraulic grippers achieve their strength from pumps that can provide up to 2000psi.
Although they are powerful, hydraulic grippers are more messy than other grippers due to the fact that oil is used in the pumps. They may also require additional maintenance due to the gripper being damaged because of the amount of force generated during the application.
The servo-electric gripper is popular in industry due to the fact that it is easy to control and manipulate. Electric motors control the movement of the gripper jaws which means the grippers are highly flexible and allow for different material tolerances when handling parts. Servo-electric grippers can also prove to be very cost effective because they are clean and have no air lines.
Despite the number of grippers available on the market, design engineers need to consider that there are still many tasks that are difficult for robots to accomplish when developing this technology. For example, commonplace industrial grippers were designed to be task-specific, which means they are not particularly versatile, and this could frustrate their wider application.
Alongside the development of industrial grippers, universities and researchers were developing technology that mimicked the human hand. This technology was challenging to develop, expensive and used a lot of power.
Design engineers around the world have already driven incredible advances in robot grippers and these two worlds are now colliding. We now have technology that is affordable, energy efficient and flexible and is able to overcome many of the traditional challenges.
Historically, it has been difficult for a robot to handle fragile objects with the correct amount of force. For instance, a robot handling fruit for a food and beverage company has to hold items firmly enough so that the fruit doesn’t slip out of its grip but gently enough that items are not crushed or bruised. To get around this, engineers are developing grippers that can handle fragile objects with the correct amount of force without dropping or breaking them, often by using softer materials.
The softness of human hands allows for compliant contact where our fingers mould against the surface of an object, but this is not fundamental to a robot’s grippers, which are traditionally made of metal or other hard materials. Another challenge for robot grippers is to adapt to what they are touching or feeling — something which comes naturally to humans.
However, designers are working to expand the applications of robots into environments where fragile objects are handled often. Soft robotics is a subfield of robotics involving robots that are made with compliant materials, similar to living organisms ― be it the tentacles of an octopus or the fleshy fingers of a human hand.
One start-up working in this area is Ubiros, who has developed an innovative electrically actuated gripper known as Gentle. The gripper has a soft enough touch that it can arrange flowers in a vase without damaging them. The electric actuation delivers more precise control than a typical pneumatic device.
Beyond the Human Hand
Another important challenge for gripper technology design was and is – dexterity. Many traditional gripper designs have two or three fingers – generally made of stiff material. Although effective for picking and placing tasks, they are not well suited to more complex manipulation activities. To enable robots to complete tasks that require more dexterity, engineers have been developing technology that more closely resembles the human hand.
One example of this is the RBO Hand 2, a human-like hand with five silicone fingers, which has been developed by researchers at the Technical University Berlin. The fingers on this hand are controlled by pressurised air, which causes them to curl and straighten when carrying out particular tasks.The design means that it can create complex geometries, mechanically adapt to the shape of an object and has low impact energy.
Another example of a company developing soft robotics based on the human hand is the Shadow Robot Company, one of Britain’s longest-running robotics firms. The company specialises in grasping and manipulation for robots and has developed the Dexterous Hand, with 20 actuated degrees of freedom, absolute position and ultra-sensitive touch sensors. The device is therefore suitable for automated tasks that require a close approximation of the human hand.
Ambidextrous gripping robots are just one example of advancing gripper technology. Developments and advances in soft robotics now mean that robots are overcoming traditional challenges and moving into new fields.
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