Setting up a real-time hardware communication for applications such as precise motion control can be timeconsuming and confusing. Therefore, a tutorial on the deployment of an EtherCAT protocol is introduced. In this article, the authors situate EtherCAT, briefly discuss the origins and working principles, and mention advantages over other widely used protocols. Additionally, the main objectives of the tutorial and the required software to complete it are presented. Online supplements are included with this article, explaining all steps to run a Simulink model in real-time on a Windows machine within a few hours.

BackgroundHere we present how the CYBERLEGs Beta-Prosthesis was modified with a new control system to participate in the Powered Leg Prosthesis event, and to report on our experience at the CYBATHLON 2016 which was held in Zurich, Switzerland in October 2016. The prosthesis has two active degrees of freedom which assist the user with extra joint power at the knee and ankle to complete tasks. The CYBATHLON is a championship for people with disabilities competing in six disciplines, using advanced assistive devices. Tasks for CYBATHLON 2016 were chosen to reflect everyday normal task such as sitting and standing from a chair, obstacle avoidance, stepping stones, slope walking and descent, and stair climbing and descent.MethodsThe control schemata were presented along with the description of each of the six tasks. The participant of the competition, the pilot, ran through each of the trials under lab conditions and representative behaviors were recorded.ResultsThe VUB CYBERLEGs prosthesis was able to accomplish, to some degree, five of the six tasks and here the torque and angle behaviors of the device while accomplishing these tasks are presented. The relatively simple control methods were able to provide assistive torque during many of the events, particularly sit to stand and stair climbing. For example, the prosthesis was able to consistently provide over 30 Nm in arresting knee torque in the sitting task, and over 20 Nm while standing. Peak torque of the device was not sufficient for unassisted stair climbing, but was able to provide around 60 Nm of assistance in both ascent and descent. Use of the passive behaviors of the device were shown to be able to trigger state machine events reliably for certain tasks.ConclusionsAlthough the performance of the CYBERLEGs prosthesis during CYBATHLON 2016 did not compare to the other top of the market designs with regards to speed, the device performed all of the tasks that were deemed possible by the start of the competition. Moreover, the Pilot was able to accomplish tasks in ways the Pilot’s personal microcontrolled prosthesis could not, with limited powered prosthesis training. Future studies will focus on decreasing weight, increasing reliability, incorporating better control, and increasing the velocity of the device. This is only a case study and actual benefits to clinical outcomes are not yet understood and need to be further investigated. This competition was a unique experience to illuminate problems that future versions of the device will be able to solve.

The Mechanically Adjustable Compliance and Controllable Equilibrium Position Actuator (MACCEPA) is a Variable Stiffness Actuator (VSA) where both equilibrium position and stiffness of the actuator can be controlled independently. It uses only one linear spring and has a simple design but its compactness is limited by the spring. For this reason a MACCEPA utilizing torsion spiral springs was designed, reducing the planar dimensions of the actuator. Torsion spiral springs are placed around the joint axis, allowing a more compact VSA in comparison to previous designs. To the authors' best knowledge, this is the first VSA based on torsion springs. This paper firstly presents the design of the actuator as the static equations and secondly discusses the design and production of the torsion spiral springs. The newly presented actuator is built and experiments are conducted to validate the model and feasibility of the torsion MACCEPA.

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