A new study has shown that more dynamic control over robotic movements can bring big power savings.

The engineering lab at the Polytechnic University of Valencia (UPV) has analysed a new way of propelling movements for robots in a more energy-efficient way.

In some cases energy consumption was cut by up to 40 per cent, by loosening digital controls.

To control a robotic arm, for example, an electric motor is used to drive upward and downward movements.

Orders are sent from a digital controller to the motor so that the joint can perform its movements.

Unai Ugalde-Olea, lecturer in the Department of Electronics Technology at UPV says this is where some savings can be a made, with a bit of intelligent programming.

“The motors need to receive orders constantly. In fact, the motor has to know at all times what angle its axis has to be,” he said.

“However, current digital controllers only issue orders at specific moments (in discrete time); they can be described as issuing orders by means of pulses: first an order, then a brief pause, then another order, another brief pause... and so on.”

The UPV research team has come up with a new proposal for this time interval in which there is no order.

In many industrial systems as long as no fresh order is issued, the previous order remains valid.

In other words, until the new control order arrives, the previous one is executed.

“In this study we have concluded that this way of working can be changed. We have used a polynomial function based on two values [which correspond to the two most recent orders] to reconstruct the process in some way,” explained Ugalde.

“This is in fact what is new about the research.”

The recent study aimed to verify the advantages that could be gained from taking both previous and new orders into consideration.

The method of computer thinking is known as fractional-order reconstruction, and despite being well known, it has not been taken into consideration in this way.

Ugalde has found that the polynomial or fractional order reconstructions may be of interest in flexible joints, as in the case of robot elbows and wrists.

In fact, lab tests showed that “the energy needed to drive the motors is considerably reduced. In ideal cases this reduction could be up to 40% without losing precision in the anticipated path,” explained Ugalde.

The tests were carried out in the lab and on a small-scale prototype, in other words, in ideal conditions.

“The next step would be to check whether it is possible to achieve similar savings on an industrial scale. In any case, even if the savings are lower, in view of the cost of electrical power, it would be a significant step forward,” added the UPV researcher.

More details are available in an article published by the journal Control Engineering Practice.