Outlook R&D – Grant project PIA

The PIA project, “Polymer Integration Actuator”, aims to make novel polymer actuators useful for a wide range of applications.
EAP (electroactive polymers) promise low-cost, energy-efficient, recyclable actuation without the use of e.g. rare earths (electric motors). Unfortunately, EAPs alone, in their current form, offer only low energy density, which limits their widespread use.

EAPs are modified in the PIA project in such a way that they can provide a power of more than 10 W. The resulting actuator is to be coupled with a microfluidic integrator in order to offer a compact, weight-optimised actuator for a wide range of applications with high force and displacement requirements.

The combination of previously hardly usable EAP and the MetisMotion core competence microfluidic integrators therefore enables completely new actuator properties:

• High force density and good miniaturisability based on standard EAP actuator unit
• High efficiency
• Fully recycable
• Independence from rare earths or RoHS relevant pollutants

This is how we extend already existing properties of our naXture technology:

• High Stiffness
• Variable Impedance
• and many more

Currently, electromagnetic drives are predominantly used for microdrives. These consist of a motor and a miniature gearbox to increase the torques or forces or reduce the speed. These have the advantage of lower costs due to the high quantities produced. However, one disadvantage of these drives is that the force density is low. In addition, the robustness is very limited, especially when mechanical impulses act on the drive from the outside. Furthermore, the efficiency of electromagnetic drives is very low due to the high Joule effect (current heat law) in the power class considered (<30W).

Pneumatic drives are also state of the art. These have cost advantages and can in principle be scaled well. However, they require a supply by means of hoses and pipes, compressed air generation via a pump and control by means of valves, which results in high installation space requirements. In addition, the stiffness is low and compared with other actuator concepts, the resulting forces are significantly smaller.

In addition, the controllability of pneumatic actuators is a major challenge. Pneumatic actuator systems also only have an average electro-mechanical efficiency of 10-15% and are therefore in many cases no longer usable in the long term when sustainability aspects are taken into account.

In addition, pneumatic drives cause high maintenance costs, as well as environmental pollution from oil dust, as oil is often added to the air during compression.

Pneumatic drives are therefore increasingly being replaced by electric drives in many applications. Examples of this are the aviation and automotive industries, as well as automation technology – especially gripping technology.

1) The energy efficiency for non-linear force/displacement requirements:
While electromagnetic drives have high efficiency for linear force/displacement relationships, this is massively reduced as soon as non-linear characteristics are required. However, this contradicts the nature of a large number of applications (e.g. gripping objects).
Currently, this causes, on the one hand, an oversizing of drives (they become large and heavy) and, on the other hand, a massive problem in terms of thermal management of systems. Cooling devices become necessary and further increase the complexity of the system.
PIA provides nearly constant low losses independent of the linearity of the force/displacement characteristics. This means that significantly smaller actuators can be installed and thermal problems can be avoided right from the start.
In addition, the low losses ensures better usability in battery-powered mobile systems. This opens up new fields of application in robotics that are not yet economically feasible today.

2) The variable stiffness of the system:
Today, electric motor and pneumatic systems quickly reach their limits when it comes to the adjustability of stiffnesses or softnesses of systems. However, it is often necessary, especially in robotics and automation technology, to be able to adjust how “stiff” a system reacts during human-machine interaction or contact with objects in order to protect both the system and the human or manipulated object from each other and prevent damage or injury.
This property plays a key role in the acceptance of autonomous systems – the user must be able to rely on not being hurt by the system, and the system must be able to survive its environment, and unforeseen situations, without damage.