Model Predictive Control of a Feedback-Linearized Hybrid Neuroprosthetic System With a Barrier Penalty

Functional electrical stimulation (FES) is prescribed as a treatment to restore motor function in individuals with neurological impairments. However, the rapid onset of FES-induced muscle fatigue significantly limits its duration of use and limb movement quality. In this paper, an electric motor-assist is proposed to alleviate the fatigue effects by sharing work load with FES. A model predictive control (MPC) method is used to allocate control inputs to FES and the electric motor. To reduce the computational load, the dynamics is feedback linearized so that the nominal model inside the MPC method becomes linear. The state variables: the angular position and the muscle fatigue are still preserved in the transformed state space to keep the optimization meaningful. Because after feedback linearization the original linear input constraints may become nonlinear and state-dependent, a barrier cost function is used to overcome this issue. The simulation results show a satisfactory control performance and a reduction in the computation due to the linearization.

A Nonlinear Dynamics-Based Estimator for Functional Electrical Stimulation: Preliminary Results From Lower-Leg Extension Experiments

Miniature inertial measurement units (IMUs) are wearable sensors that measure limb segment or joint angles during dynamic movements. However, IMUs are generally prone to drift, external magnetic interference, and measurement noise. This paper presents a new class of nonlinear state estimation technique called state-dependent coefficient (SDC) estimation to accurately predict joint angles from IMU measurements. The SDC estimation method uses limb dynamics, instead of limb kinematics, to estimate the limb state. Importantly, the nonlinear limb dynamic model is formulated into state-dependent matrices that facilitate the estimator design without performing a Jacobian linearization. The estimation method is experimentally demonstrated to predict knee joint angle measurements during functional electrical stimulation of the quadriceps muscle. The nonlinear knee musculoskeletal model was identified through a series of experiments. The SDC estimator was then compared with an extended kalman filter (EKF), which uses a Jacobian linearization and a rotation matrix method, which uses a kinematic model instead of the dynamic model. Each estimator's performance was evaluated against the true value of the joint angle, which was measured through a rotary encoder. The experimental results showed that the SDC estimator, the rotation matrix method, and EKF had root mean square errors of 2.70°, 2.86°, and 4.42°, respectively. Our preliminary experimental results show the new estimator's advantage over the EKF method but a slight advantage over the rotation matrix method. However, the information from the dynamic model allows the SDC method to use only one IMU to measure the knee angle compared with the rotation matrix method that uses two IMUs to estimate the angle.

A Modified Dynamic Surface Controller for Delayed Neuromuscular Electrical Stimulation

A widely accepted model of muscle force generation during neuromuscular electrical stimulation (NMES) is a second-order nonlinear musculoskeletal dynamics cascaded to a delayed first-order muscle activation dynamics. However, most nonlinear NMES control methods have either neglected the muscle activation dynamics or used an ad hoc strategies to tackle the muscle activation dynamics, which may not guarantee control stability. We hypothesized that a nonlinear control design that includes muscle activation dynamics can improve the control performance. In this paper, a dynamic surface control (DSC) approach was used to design a PID-based NMES controller that compensates for EMD in the activation dynamics. Because the muscle activation is unmeasurable, a model based estimator was used to estimate the muscle activation in realtime. The Lyapunov stability analysis confirmed that the newly developed controller achieves semi-global uniformly ultimately bounded (SGUUB) tracking for the musculoskeletal system. Experiments were performed on two able-bodied subjects and one spinal cord injury subject using a modified leg extension machine. These experiments illustrate the performance of the new controller and compare it to a previous PID-DC controller that did not consider muscle activation dynamics in the control design. These experiments support our hypothesis that a control design that includes muscle activation improves the NMES control performance.

A semi-active hybrid neuroprosthesis for restoring lower limb function in paraplegics

Through the application of functional electrical stimulation (FES) individuals with paraplegia can regain lost walking function. However, due to the rapid onset of muscle fatigue, the walking duration obtained with an FES-based neuroprosthesis is often relatively short. The rapid muscle fatigue can be compensated for by using a hybrid system that uses both FES and an active orthosis. In this paper, we demonstrate the initial testing of a semi-active hybrid walking neuroprosthesis. The semi-active hybrid orthosis (SEAHO) supports a user during the stance phase and standing while the electric motors attached to the hip section of the orthosis are used to generate hip flexion/extension. FES in SEAHO is mainly used to actuate knee flexion/extension and plantar flexion of the foot. SEAHO is controlled by a finite state machine that uses a recently developed nonlinear controller for position tracking control of the hip motors and cues from the hip angle to actuate FES and other components.

Further Results on Predictor-Based Control of Neuromuscular Electrical Stimulation

Electromechanical delay (EMD) and uncertain nonlinear muscle dynamics can cause destabilizing effects and performance loss during closed-loop control of neuromuscular electrical stimulation (NMES). Linear control methods for NMES often perform poorly due to these technical challenges. A new predictor-based closed-loop controller called proportional integral derivative controller with delay compensation (PID-DC) is presented in this paper. The PID-DC controller was designed to compensate for EMDs during NMES. Further, the robust controller can be implemented despite uncertainties or in the absence of model knowledge of the nonlinear musculoskeletal dynamics. Lyapunov stability analysis was used to synthesize the new controller. The effectiveness of the new controller was validated and compared with two recently developed nonlinear NMES controllers, through a series of closed-loop control experiments on four able-bodied human subjects. Experimental results depict statistically significant improved performance with PID-DC. The new controller is shown to be robust to variations in an estimated EMD value.

German Environmental Survey (GerES): Human biomonitoring as a tool to identify exposure pathways

The German Environmental Survey (GerES) is a representative population study and has been repeatedly carried out since the mid-1980s. The currently run survey (GerES IV) is the first one solely targeted on children. The GerES IV Pilot Study resulted in first insights into major exposure pathways relevant to children. These insights were made possible by the determination of pollutant concentrations in blood and urine and the additional consideration of their occurrence in the indoor environment and by using questionnaire data. The results of the GerES IV Pilot Study are presented according to major exposure pathways such as house dust, food and environmental tobacco smoke (ETS). An overview on relevant pilot study results is given. The results of GerES IV will permit the verification and substantiation of the pilot study results.

Towards the development of molecularly imprinted polymer based screen-printed sensors for metabolites of PAHs

This paper describes the fabrication of a sensor for 1-hydroxypyrene (1-OHP) based on a screen-printed carbon electrode (SPCE) modified with a molecularly imprinted polymer (MIP); 1-OHP was chosen as a model metabolite of polyaromatic hydrocarbons (PAHs). It was shown that 1-OHP could be readily oxidised at a plain SPCE and the electrochemical mechanism was found to involve an ECE (electron transfer-chemical reaction-electron transfer) process. The MIP for 1-OHP was prepared using only divinylbenzene (DVB) and styrene as monomers and the binding was only based on hydrophobic interactions. Batch binding studies revealed that optimum uptake of 1-OHP by the MIP occurred from solutions containing 35% water in methanol. Selectivity of the binding sites in the MIP was examined by performing uptake studies in the same solution containing either phenol or 1-naphthol; the specific binding of 1-OHP was twenty times greater than the former and five times greater than the latter. Preliminary calibration studies were performed with the MIP-SPCE using a two-step approach; accumulation was carried out in 35% water in methanol followed by measurement in 50% methanol-0.025 mol dm(-3) phosphate buffer pH 12. This two-step non-competitive affinity assay gave encouraging results and indicated potential for use in pollution studies.

Effect of lateralized kinetic visual cues on visual search in patients with unilateral spatial neglect

Patients with left neglect following right cerebral infarcts and normal control subjects searched for a single target letter among distractor letters presented on a display screen while kinetic visual cues were continuously presented on the left side or the center of the display screen. Kinetic visual cues presented on the left side enhanced patients' detection of left-sided targets but did not reduce the time that they required to search for left-sided targets. In contrast, the same cues did not alter the patients' detection or rate of search for left-sided targets when they were presented in the center of the display screen. Analysis of these and previous results suggest that kinetic visual cues may be more suitable than other forms of cueing for rehabilitation of neglect and may be particularly effective with neglect patients whose attention is strongly biased to the unneglected side.

Coping with the late effects: differences between depressed and nondepressed polio survivors

This study examined differences between depressed and nondepressed individuals with a history of paralytic poliomyelitis in terms of demographics, health status and coping strategies. The prevalence of distress and depression in this group of 116 polio survivors was determined. Subjects completed the Brief Symptom Inventory, the Coping with Disability Inventory and a questionnaire concerning their polio histories and self-perceptions of health. Medical assessments were performed by physicians. Only 15.8% of the sample had scores indicating depression and elevated distress. Depressed/distressed polio survivors were more likely to: be living alone, be experiencing further health status deterioration, seek professional help, view their health as poor, report greater pain, be less satisfied with their occupational status and their lives in general and exhibit poorer coping outcome behaviors in relation to their disability. Three factors in coping with the late effects of polio were identified through a factor analysis of the Coping with Disability Inventory: positive self-acceptance, information seeking/sharing about the disability and social activism. Differences between depressed/distressed and other polio survivors were found across these three factors, with depressed/distressed subjects having significantly lower coping scores. These and other results are discussed.

Prevalence and associated features of depression and psychological distress in polio survivors

This cross-sectional study examines the prevalence of psychological distress and depression among 116 polio survivors. It investigates demographic, medical, and coping differences between subjects with (n = 17) and without (n = 99) these symptoms. Subjects were administered the Brief Symptom Inventory (BSI), the Coping with Disability Inventory (CDI), and a questionnaire about their polio histories. The BSI provided measures of psychological distress and depression that defined the subgroups. The CDI assessed coping behaviors. BSI scores for the overall sample were within the normal range indicating no major distress, depression, nor elevated somatic complaints. Several significant differences were found between the two subgroups. On average, depressed/distressed subjects reported an increase in pain (p < .01) and further deterioration of their medical status since the time of their physical best subsequent to the onset of polio (p < .01). They consistently rated their health as poorer than did nondepressed/nondistressed subjects (p < .001). They also reported less satisfaction with life and their occupational status (p < .001) and displayed poorer coping behaviors combined (p < .001). Selected variables such as life satisfaction, pain, decrease in activity, and current living situation accounted for 51% of the variance when predicting distress and depression among this group of polio survivors.

Combined and separate effects of eye patching and visual stimulation on unilateral neglect following stroke

In Experiment 1, 11 of 13 stroke patients with left-sided neglect benefitted from monocular patching in at least one (of five) tests of neglect. This beneficial effect in most cases was limited to the period when the patch was worn. In Experiment 2, another group of stroke patients (n = 18) with left-sided neglect were tested in a line-bisection task with monocular patching and/or lateralized visual stimulation--a procedure previously shown to reduce neglect. Each procedure resulted in substantial benefits; the two procedures combined resulted in significantly larger benefits than either alone. As in Experiment 1, the degree of benefit of patching (alone or in combination with stimulation) was not related to several demographic factors. These findings suggest that monocular patching, together with lateralized visual stimulation, may significantly reduce neglect in daily activities and may be more beneficial than procedures requiring patients to be aware of their disorder and to use strategies for scanning the neglected side.

[Erectile dysfunction following pelvic fracture and pelvic trauma]

In the course of this research a questionnaire was submitted to 209 male patients who had been treated in the surgical university clinic of Erlangen between 1976 and 1985, in order to get knowledge about possible complications in the form of erectile non-functioning. 29 of these patients had died in the meanwhile, 32 had moved to an unknown address. Among the other 148, 86 were willing to give some information. 44% of these people turned out to be suffering from an impotentia coeundi. Furthermore, we were able to prove that 40% of those patients for whom a large haematoma of the pelvis had been diagnosed were impotent. Finally, 73% of the patients who had additionally suffered an injury of the urogenital canal turned out to be impotent. On closer examination of the urogenital side-effect case of rupture of the bladder and as much as 87.5% in the case of lesions of the urethra. In connection with the urethra lesions reference is made to the controversial discussion about their therapy, with dichronous recanalling clearly being given preference as it involves considerably fewer complications compared to primary recanalling.

Altitudinal neglect following traumatic brain injury: a case report

We present an analysis of altitudinal neglect in a patient who following traumatic brain injury showed extinction to a visual stimulus presented in the lower field when another stimulus was simultaneously presented in the upper field. When estimating the midpoint of vertically-oriented rods presented below eye level using visual cues, tactile/kinesthetic cues or a combination of these cues, she consistently pointed higher than control subjects did. She showed less severe impairments when the rods were presented at or above eye level. When estimating the midpoint between two clicks presented above and below her head, she pointed higher than did control subjects. These deficits cannot be accounted for by sensory or motor disorders and appear to be due to a disorder in attending to stimuli in the lower half to space.

Assessment of distractibility in auditory comprehension after traumatic brain injury

In a simulated functional task involving comprehension of a spoken passage, the performance of 20 traumatically brain-injured and 14 non-brain-injured control patients was compared under conditions which included the presence and absence of competing vocal stimuli. The subjects heard 10 target paragraphs which were approximately 1 minute in length. Five of these paragraphs were transmitted without any interference, while the other five were presented with distraction caused by a second voice reading a different paragraph with equal volume and intensity. Based on the answers to subsequent multiple-choice questions, the traumatically brain-injured subjects had significantly more difficulty comprehending the target passages in the presence of the interfering or competing passages compared to control subjects. The results of this study suggest the need for specific rehabilitation programmes to aid brain-injured persons in improving their auditory comprehension in everyday situations where distracting or competing auditory stimuli are present.

Atypical fibroxanthomas of the skin: multiple primaries

An 83-year-old man experienced, within a four-year span, two separate atypical fibroxanthomas occurring on the right ear and right forehead without any satellite lesions or obvious lymph node metastases. Such an occurrence has not been reported before.

Low-sulfur hair syndrome associated with UVB photosensitivity and testicular failure

A 16-year-old male patient had a syndrome that included growth retardation, mental retardation, hair shaft abnormalities, neurosensory hearing loss, contractures of the fifth fingers, ultraviolet B (UVB) photosensitivity, small testicular size, and elevated levels of follicle-stimulating hormone. Reduced hair sulfur content and a characteristic pattern of light and dark birefringent bands, seen when hairs were viewed with polarization microscopy, were typical of the low-sulfur hair syndrome. UVB photosensitivity and testicular failure have not previously been identified as components of this syndrome.

Elastosis perforans serpiginosa induced by penicillamine

A patient with Wilson disease, under prolonged treatment with penicillamine, developed lesions of elastosis perforans serpiginosa (EPS). Examination of biopsy specimens by light microscopy revealed the characteristic changes of EPS. Examination by transmission electron microscopy revealed structural changes in the elastic fibers not previously described. The appearance of the lesions by scanning electron microscopy is described for the first time. It is suggested that penicillamine induced EPS may be morphologically distinct from the idiopathic form.

Dapsone-induced motor polyneuropathy. A complication of prolonged treatment of subcorneal pustular dermatosis

A motor polyneuropathy developed in a woman with subcorneal pustular dermatosis of 16 years' duration, who had received at least 300 gm of dapsone over a five-year period and 80 gm during the four-month period of progression of her neurologic symptoms. Although the patient believed her muscle power had returned to normal four months after the drug was stopped, a slight peripheral neuropathy remained. Electrodiagnostic and clinical features during the period of greatest weakness and the subsequent 16 months were consistent with a polyneuropathy of the axonal type. The neurotoxicity of dapsone appears to be dose-dependent, but the mechanism by which it occurs is unknown.