Fluid power: the key to comprehensive automation
06 May 2015
Chris Buxton argues that hydraulic and pneumatic technologies are an essential complement to electromechanical drives as UK manufacturing continues to embrace automation.
The benefits of automation within UK manufacturing are thankfully becoming better recognised than has been the case over the past ten years. What is less well recognised is the inextricable link between this technology and the enabling role played by fluid power.
Greater accuracy, increased precision, faster operation, increased quality, greater consistency and significant cost savings are just a few of the benefits to be realised through automation but they all rely upon some form of actuation derived from either electromechanical, hydraulic or pneumatic technology.
For many automation applications electric drives are the technology of choice. However there are vast numbers of applications where hydraulics are pertinent to heavy duty applications whilst pneumatic technology is chosen for lightweight, high speed and comparatively low cost applications.
Take the relationship between robotics and pneumatics. Every system is likely to have some level of pneumatics installed to facilitate clamping, holding or actuating. Typically, a robot has some form of tooling on its arm and that tooling is equipped with either single pneumatic or electronic actuators, or a manifold with multiples fitted. If the power requirements increase then the electronic or electromechanical options can prove to be fairly bulky and expensive.
Consequently, for a factory requiring a reasonably affordable, clean, lightweight system that is fairly easy to apply, then pneumatics often ‘wins the day.’ In the case of hydraulics, this is normally used for tasks where there is a need to handle heavy parts such as billets of steel, or when there is a need for extra force in gripping such components. Some BFPA members offer tailored systems in cases where the weight and forces involved in certain applications dictate the need for hydraulics that can deliver the required forces.
Indeed, gripping is one of the most common functions in robotics applications. Pneumatic technology is used not exclusively, but frequently to give a robot ‘pick-and-place’ capability, either using vacuum or pneumatics as the mechanism for closing the mechanical gripper. The reasons for this are partly cost and partly weight-related. Pneumatic devices weigh less than servomotors and therefore one can use smaller robots for the equivalent task. Pneumatic technology is also regularly used for fixing and tooling; for example, for holding parts in place to allow robots to perform the functions that are required.
In the not too distant past, many people were expecting electric drives to take over completely from fluid power; this has not happened. One reason is that the performance of hydraulics and pneumatics has improved markedly in the last decade. There are also cost and weight benefits to be realised, particularly with pneumatics, so fluid power still has a very important role to play in almost every sector.
Engineers designing automation systems will choose the most appropriate drive method to achieve what is required of their machine or process, whether it be hydraulic, pneumatic or electromechanical. Most automated systems can best be operated with a combination of all three technologies. Once again, the ultimate choice comes down to factors such as cost and weight, as well as the desired level of performance.
At one time, pneumatic technology was rarely used for on/off-type applications because pneumatic actuators didn’t generally offer the servo control capabilities of electric drives. However, that has now changed and companies can now achieve this level of performance from modern pneumatics.
The concept of artificial intelligence (AI) is often referenced within the context of robotics. However, many researchers use the related and complementary term of ‘intelligence amplification’ (IA). For example, there is a form of remote hand-like device called a tele-factor, tele-manipulator or ‘waldo’, which, through the use of hydraulics and electronics, allows a mechanism to be operated by a human. Uses for this type of device might, for example, include moving dangerous materials or liquids.
Cinematic productions such as ‘Alien’ and ‘Avatar’ have made use of this technology. In the former the heroine fits into what could be described as a full body-suit version of a waldo – a large metal frame which is able to amplify her strength. Researchers believe that there are great opportunities for this type of technology to be adapted and applied within industry or in the service sectors.
One area where control technology is seeing swift change is mechanical compliance - compliance in the sense of being highly adaptable during normal operation; for example, systems that offer variable stiffness. Within the context of fluid power, this relates more to pneumatics than to hydraulics. If one considers a robotic arm that works on the principle of antagonistic pairs – similar to human skeletal muscles that work in groups; as one muscle contracts another relaxes.
Systems that work with humans, for example, will need to be designed to be intrinsically compliant or have a control fitted that makes one that is non-compliant, compliant. Similarly, one might need to lift objects which themselves are compressible or delicate. The compliance available in, for instance, pneumatics could be explored more in this area.
It is easy to be myopic in the world of robotics, but there are some big changes taking place in the way that robotic systems will be used in a variety of applications and fluid power, whether hydraulic or pneumatic, will play a key enabling role as we move forwards into the future.
Chris Buxton is CEO of the British Fluid Power Association
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