Douwe Dresscher

Inertia-driven controlled passive actuation

A serious problem with using electrical actuators in legged locomotion is the significant energy loss. For this reason, we propose and analyse an alternative means of actuation: Controlled Passive Actuation. Controlled Passive Actuation aims at reducing the energy flow through electric actuators by actuating with a combination of an energy storage element and a Continuously Variable Transmission. In this work, we present a method where we apply a Continuously Variable Transmission with a storage element in the form of a mass to change the state of another mass (“the load”). An abstraction layer is created to abstract the inertia-driven Controlled Passive Actuation to a source of effort, a force actuator. On this abstracted system, feedback control can be applied to achieve control goals such as path tracking. With simulations and experiments, we show that inertia-driven Controlled Passive Actuation can be used to control the state of an (inertial) load. The experimental results show that the performance of the system is affected by the internal dynamics and limited rate of change of the transmission ratio of the Continuously Variable Transmission.

Motor-gearbox selection for energy efficiency

Energy consumption of robotic systems is getting more and more attention. Previous work suggests that energy losses in the actuators of robots are a significant source of high energy consumption. A possible reason is that, so far, motor-gearbox selection methods have not focussed on energy efficiency. In this work, we present a model-based motor-gearbox selection procedure with the focus on key mechanisms of energy dissipation. Using an example, we evaluate the possible efficiency gains when selecting a motor-gearbox combination for energy efficiency. In this example, the losses are reduced by 56% to 40%. We conclude that selecting a motor-gearbox combination for energy efficiency can provide a significant improvement in the efficiency. However, the energy losses in the motor-gearbox combination remain significant.

Autonomous Exploration Using Kinect and Laser Range Finder

This paper analyzes the Kinect limitationa and proposes a system setup equipped with both Kinect and laser range finder.

Controlled passive actuation: concepts for energy efficient actuation using mechanical storage elements and continuously variable transmissions

Walking robots consume more energy for locomotion than their wheeled and tracked counterparts. To achieve energy autonomous operation, a robot needs to run on energy that is harvested from its environment. In this light, it is meaningful to address reduction of energy consumption. The contribution of the research discussed in this thesis is twofold. Firstly, we increase insight in the mechanisms of energy loss by supplementing prior work with an analysis of the energetic losses in electric actuators. Secondly, we made steps towards the reduction of energy losses by including a mechanical storage element (a spring or flywheel) and a Continuously Variabel Transmission. We have named this actuation concept Controlled Passive Actuation and experimented with two setups to prove the concept. As part of this effort, two novel designs of Continuously Variable Transmissions are discussed.

A novel concept for a translational continuously variable transmission

Continuously Variable Transmissions have the potential to change robotics. When used in a drive train in combination with a spring, they could significantly reduce energy consumption. However, so far these advantages have been shown in theory only. To exploit the concept of a Continuously Variable transmission to its full potential it should have certain properties and be designed with some critical design points in mind. In this work, we propose three properties that a Continuously Variable Transmission needs to have and two critical design points that should be optimised in a design. We propose a novel concept of a lever with a movable pivot where the pivot always moves along the lever. A realisation of this concept is discussed and evaluated with respect to the required properties and critical design points. We conclude that the realisation has the required properties and that the performance on the critical design points can be improved by improving the mechanical design.

Applying energy autonomous robots for dike inspection

This article presents an exploratory study of an energy-autonomous robot that can be deployed on the Dutch dykes. Based on theory in energy harvesting from sun and wind and the energy-cost of locomotion an analytic expression to determine the feasible daily operational time of such a vehicle is composed. The parameters in this expression are identified using lab results and weather statistics. After an evaluation of the “Energy autonomous robot in the Netherlands” case, the results are generalised by looking at the effects of varying the assumptions. Based on this work, three conclusions can be drawn. Firstly, it is realistic to have an energy-autonomous walking dyke robot in the Netherlands. Secondly, the use of solar panels is probably not feasible if the amount of solar energy that is available is much less than assumed in the study. Finally, in this case study, the inclusion of a wind turbine typically offers a slight benefit. Furthermore, it gives a significant benefit in the months where the incident power of the sun is low, thus allowing a reasonable operational time during the winter.