Fluid power: Key to automation
05 May 2015
Hydraulic and pneumatic technology are an essential compliment to electromechanical drives in ensuring the inexorable march towards automation within UK manufacturing, according to Chris Buxton, CEO of the British Fluid Power Association (BFPA)
The benefits of automation are becoming better recognised than has been the case over the past 10 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 myriad of benefits to be realised through automation, but they all rely upon some form of actuation derived from electromechanical, hydraulic or pneumatic technology.
For many automation applications electric drives are the technology of choice. However there are vast numbers of applications where pneumatics and hydraulics are the preferred solution. Hydraulic technology is particularly pertinent to heavy duty applications where high power is required whilst pneumatic technology is chosen for lightweight, high speed and comparatively low cost applications. The latter also offers benefits in clean environments such as the food or electronics sectors.
In considering the pneumatics world, the relationship between robotics and pneumatics is very strong. From a complete solution perspective every system is likely to have some level of pneumatics on it to facilitate clamping, holding or actuating something and the sequencing of this type of operation within the process is critical. Typically, a robot has some form of tooling on its arm and that tooling is equipped with 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, in a factory requiring an affordable, clean, lightweight solution that is fairly easy to apply, pneumatics often ‘wins the day.’
In the case of hydraulics, the technology 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. Usually, robot integrators become involved in hydraulics when supplying automation equipment to some of the larger OEMs and for manufacturers of heavy prime materials. There are BFPA members who can offer tailored solutions in cases where the weight and forces involved in certain applications dictate the need for hydraulic systems that can deliver what are often tremendous forces.
In the Service robot sector, (those robots that tend to emulate humanoid structure and activity), many high performance robots have relied upon hydraulic actuation with all the power gain advantages on offer. Similarly, pneumatic actuators are used as an effective means of translating the force of compressed air into an effective form of motion control. While many pieces of plant and equipment still need to be operated manually, increasing use of controllers means that more equipment can now be operated in an autonomous or semiautonomous manner.
As part of their R&D remit, many academic institutions involved in automation & robotics are seeking to make systems smaller and more energy efficient. They consider opportunities in existing and new markets for systems that are lighter and more energy efficient – for example, those that are fitted with smaller and less obtrusive compressor units. However, it largely comes down to market drivers. If one company develops a more compact but equally efficient system it could open up a wider market for similar types of product. Many pundits believe that this would be a good area in which fluid power companies should invest some of their R&D budget.
In terms of the different types of robotic applications, gripping is a common function. In such applications pneumatic technology is used not exclusively but very 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 application.
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. There are also applications where particularly strong gripping forces are required; in the foundry industry for example, for picking up hot billets. In these types of applications hydraulics is often the only technology that can be deployed.
In the not too distant past, many people were expecting electric drives to take over completely from Fluid power. In practice, this has not happened. One of the reasons for this is that the performance of hydraulics and pneumatics has improved markedly over the past 10 years. There are also cost and weight benefits to be realised, particularly with pneumatics, thus fluid power still has an important role to play in almost every sector. An engineer designing an automation system will focus upon the type of functionality required and choose the most appropriate drive mechanism to achieve what is required, 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 the weight of the mechanisms. It also comes down to the performance of the mechanisms for a given type of control that might be required. At one time, Pneumatic technology was rarely used for ‘on/off-type’ applications because pneumatic actuators didn’t generally offer the same servo control as electric drives. However, that has changed and companies can now achieve the required performance from modern pneumatics. For every application it is a case of weighing up the ‘pros and cons’ of each technology.
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. The film industry in productions such as ‘Alien’ and ‘Avatar’ 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 arena.
One area where control technology will see swift change is around the issue of compliance; compliance in the sense of being highly adaptable during normal operation – for example, systems offering 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 a non-compliant: compliant way. Similarly, one might need to lift objects which themselves are compressible or delicate. In the area of archaeology, for example, one might wish to move something heavy but fragile, such as a sarcophagus which might bend a little or be in danger of cracking when moved. The compliance available in, for instance, pneumatics could be explored more in this area.
AI and compliance
There are many existing and potential applications where AI, together with sensors and fluid power solutions, can all play a valuable part. The ‘Boston Dynamics’ ‘Big Dog’ is one such example. This rough-terrain robot has an engine that drives a hydraulic actuation system. Big Dog can walk, run, climb and carry heavy loads. Its sensors can monitor things such as hydraulic pressure, oil temperature and engine functions.
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 yydraulic or pneumatic – will play a key enabling role.