6th Dutch Bio-Medical Engineering Conference
26 & 27 January 2017, Egmond aan Zee, The Netherlands
10:30   Rehabilitation Engineering
Chair: Edsko Hekman
15 mins
Amber Emmens, Edwin van Asseldonk, Herman van der Kooij, Iolanda Pisotta, Marcella Masciullo
Abstract: Exoskeletons that are designed for people with a Spinal Cord Injury (SCI) generally rely on crutches for balance maintenance. Our goal is to enable these subjects to maintain balance in an exoskeleton without additional supporting devices, by designing proper balance controllers. Therefore, as a first step, we tested and compared various balance controllers on a powered Ankle-Foot Orthosis (pAFO) acting in the sagittal plane to assist subjects with a SCI with balancing. Two SCI subjects affected by an incomplete low lesion participated in experiments in which they had to maintain their standing balance, without stepping, while receiving perturbations on the pelvis from a robotic pushing device. We tested different controllers on the pAFO: a fixed stiffness around the ankle; a PD-controller on the Center of Mass (CoM) that controls the CoM to a reference location; and a Momentum-Based Controller (MBC) that tries to find joint torques such that a certain desired centroidal momentum is obtained [1]. The first controller operates in joint space and the latter two in CoM space. Using force plates, the torque generated by the subject was estimated and compared to the torque delivered by the pAFO, to evaluate the supportive effect of the pAFO. We found that the PD-controller on the CoM, and to lesser extent the MBC, provided a substantial assistive torque to the subjects after a perturbation had been applied. The ankle torque of the subjects decreased without worsening the balancing performance. In contrast, when a fixed ankle stiffness was implemented on the pAFO, the subjects needed to provide most of the necessary torques for balancing themselves, which shows the added value of controlling in CoM space compared to joint space. In future work, we will extend the CoM space controllers to a wearable exoskeleton with more actuated degrees of freedom
15 mins
Kyrian Staman, Herman van der Kooij
Abstract: Concept modeling and experimental validation of an electric motor driving an input cylinder connected, through a hydraulic fluid line, to an output cylinder for use in a flexible robotic suit for the restoration of human gait.
15 mins
Paul Verstegen, Erik van Oene
Abstract: People with neuromuscular diseases can benefit from dynamic arm support systems. These dynamic arm supports are used during daily life to be able to, independently, perform activities of daily living (ADL). The amount of assistance a person needs depends on the progress of the disease. The fact that the amount of assistance differs has resulted in the design of several dynamic arm support systems with specific characteristics. L. van der Heide et al.[1] show in their literature overview the commercial and non-commercial arm support systems. They have divided the arm support systems in four groups: non-actuated, passively actuated, actively actuated, and functional electrical stimulators. Taking a closer look at the actively actuated arm supports it becomes clear that there are no systems available that can be used to actively assist the elbow and shoulder. To overcome this problem other systems, that are not specially designed as an arm support system, are used in research. Corrigan et al.[2] use a HapticMASTER, as an arm support, to be able to test admittance control in an arm support system. Jobo-Prat et al.[3] use a commercial robot manipulator to perform their tests. Both show that control strategies can increase the performance of arm support systems. But to be able to increase the performance, a dedicated active arm support is required. This paper shows a novel designed and realisation of an active arm support having five degrees of freedom (DOFs). The five DOFs can be divided into two groups: three DOFs are used to mimic the shoulder, the other two DOFs are used to mimic the elbow of the human body. The active arm support is equipped with a six DOF force/torque sensor that is used as an input for the controller. For the control several design considerations have been taken into account for instance the controller bandwidth and power of the actuators. Moreover, besides the control design, also special requirements for the mechanical design of the arm support are taken into account as for instance the possibility to mount the system on an electric wheelchair. After building the system tests have been performed. As an example admittance control is implemented and combined with gravity compensation.
15 mins
Kris Cuppens, Eveline De Raeve, Tom Saey, Mario Broeckx, Ingrid Knippels, Luiza Muraru, Johan Claes, Veerle Creylman
Abstract: The design and manufacturing of foot orthoses makes mostly use of the experience based knowledge of a CPO (certified prosthetist/orthotist) or podiatrist. With the introduction of new (digital) design and additive and subtractive manufacturing techniques on the one hand, and the emphasis on evidence based practice on the other hand, there is a growing need for the quantification of the material and structure properties of foot orthoses. Quantifying foot orthosis properties permits an objective comparison between different orthoses. For the quantification of these properties, we developed a protocol that measures the compression and force at certain reference points on the orthosis using the TA-XTplus Texture Analyser (Stable Micro Systems). First a reference coordinate system is constructed based on the patient’s location of the calcaneus, the first and fifth metatarsal head and the most proximal point between the hallux and second toe. The properties of the orthosis are measured in four different zones: the heel area, the medial arch, the area of the metatarsal heads and the forefoot area. 5 to 9 points of interest, depending on the size of the area, are measured in each zone. While the orthosis is fixed to the measuring system, different loading sequences are applied to these points of interest. The loading sequences differ in the applied force, speed of compression and the total compression. With this protocol, we aim not only to quantify the cushioning effect of the orthosis, but also to determine the influence of the orthosis structure (such as the medial arch). This is particularly important for the additive manufactured orthoses, as their properties will depend on the printed structures. To test our protocol, 3 orthoses with identical shape were produced in ethylene-vinyl acetate (EVA) in low, medium and high density (shore values of 25, 50 and 70, respectively). The orthoses were designed for a patient, with a leg length discrepancy and a mild form of scoliosis. The compression set [1], compression stiffness [1] and the height were derived from the data measured using the Texture Analyser. The results confirmed the expected differences between the orthoses in cushioning abilities. Also, there were noticeable differences between zones within an orthosis, despite the fact that the orthosis was made from a single material. In a next step, we will test different orthoses designed for the same subject by different CPOs and manufactured using traditional and new techniques.
15 mins
Arvid Keemink, Richard Fierkens, Joan Lobo-Prat, Jack Schorsch, David Abbink, Jeroen Smeets, Arno Stienen
Abstract: Passive assistive devices that compensate gravity can reduce human effort during lifting and transportation of heavy objects. The additional reduction of inertial forces, which are still present during deceleration when using gravity compensation, could further increase movement performance in terms of accuracy and duration. Applying velocity dependent haptic damping forces to the user helps in reducing perceived effects of inertial forces during braking. However, how users actually respond to these damping forces, and exploit them, is unknown. The practical application of this damping is in a passive spring compensated lifting aid in which a fully passive damping mechanism is used (e.g. damping based on eddy currents). Such a method keeps the system safe due to its passive nature, while delivering haptic forces. This study investigated whether position dependent damping forces (PDD) around reaching targets could assist during planar reaching movements where users move an inertial mass of 12.5 kg with one hand. The PDD damping coefficient was position dependent and its value increased linearly from 0 Ns/m to 200 Ns/m over 18 cm (long PDD) or 9 cm (short PDD). The haptic inertial mass and damping forces were rendered on an admittance controlled Moog HapticMaster system. Movement performance of reaching with both PDDs was compared against damping-free baseline conditions and against constant damping (40 Ns/m). Using a Fitts’ like experiment design, 18 subjects (24.4±2.8 y.o.) performed a series of reaching movements with index of difficulty: 3.5, 4.5 and 5.5 bits, and distances 18, 23 and 28 cm for all conditions (i.e. 9 combinations). Results show that PDD reduced (compared to baseline and constant damping) movement times by more than 30% and reduced the number of target re-entries, i.e. increasing reaching accuracy, by a factor of 4. Results were inconclusive about whether the long or short PDD conditions achieved better task performance, although mean human acceleration forces were higher for the short PDD, hinting at marginally faster movements. Overall, PDD is a useful haptic force to get humans to decrease their reaching movement times while increasing their targeting accuracy. The results can be explained and numerically modelled by assuming that the human attempts to optimize his/her reaching movements in time but is limited by energy expenditure while being disturbed by muscle-activation dependent (i.e. multiplicative) motor noise. Since high environment damping around reaching targets attenuate the contribution of this multiplicative noise, it allows for greater reaching accuracy, which in turn allows the human to apply higher forces while maintaining the required task accuracy. Such models, together with subjective preference, would allow us to in the future develop optimal profiles for the damping coefficient over planar reaching movements.
15 mins
Stergios Verros, Arjen Bergsma, Edsko Hekman, Bart Verkerke, Bart Koopman
Abstract: The most common form of muscular dystrophy in humans is Duchenne muscular dystrophy (DMD), affecting 1 in every 3,500 boys[1]. DMD causes progressive degeneration of muscles which leads to progressive loss of muscle strength[1]. The mean age of death was 20 years but due to improved health care practices and ventilation the life expectancy is increased to 25-30 years[2][3]. By increasing the life expectancy, the function of upper extremity becomes more important for giving DMD patients more independence to perform daily tasks[4]. The loss of muscle function not only affects the arms, but it also causes instability of trunk and head. Furthermore, assisting the arm function with an assistive device, like the A-gear[5], can cause extra instability of the trunk and loss of visual feedback of the arm. So, a trunk assistive device is essential to stabilize and support the trunk during arm movements whereas a head assistive device is essential to stabilize, support and provide visual control during arm movement. Enabling stable trunk function leads to a bigger range of motion and make specific movements easier[5]. We developed a 1DoF active trunk assistive device (Trunk Drive) for people with Duchenne Muscular Dystrophy (DMD) that actively assists trunk flexion and extension. To control the Trunk Drive, EMG from trunk muscles and Force exerted from trunk as control interfaces are studied. EMG and Force have been extensively used as control interfaces in assistive devices[6][7]. In our study we investigated if people with DMD could control the Trunk Drive using the above-mentioned control interfaces and compare their performances based on a position tracking task. The results show that the Trunk Drive system is capable of supporting trunk flexion and extension using EMG and Force signals that still remain measurable. According to the results, performance differences such as speed, path efficiency and overshoot exists between EMG and Force.