Feedback control of unsupported standing in paraplegia. Part I: optimal control approach

This is the first of a pair of papers which describe an investigation into the feasibility of providing artificial balance to paraplegics using electrical stimulation of the paralyzed muscles. By bracing the body above the shanks, only stimulation of the plantarflexors is necessary. This arrangement prevents any influence from the intact neuromuscular system above the spinal cord lesion. Here, the authors extend the design of the controllers to a nested-loop LQG (linear quadratic Gaussian) stimulation controller which has ankle moment feedback (inner loops) and inverted pendulum angle feedback (outer loop). Each control loop is tuned by two parameters, the control weighting and an observer rise-time, which together determine the behavior. The nested structure was chosen because it is robust, despite changes in the muscle properties (fatigue) and interference from spasticity

Feedback control of unsupported standing in paraplegia. Part II: experimental results

For pt. I see ibid., vol. 5, no. 4, p. 331-40 (1997). This is the second of a pair of papers which describe an investigation into the feasibility of providing artificial balance to paraplegics using electrical stimulation of the paralyzed muscles. By bracing the body above the shanks, only stimulation of the plantar flexors is necessary. This arrangement prevents any influence from the intact neuromuscular system above the spinal cord lesion. Here, the authors present experimental results from intact and paraplegic subjects

Investigation of the Hammerstein hypothesis in the modeling of electrically stimulated muscle

To restore functional use of paralyzed muscles by automatically controlled stimulation, an accurate quantitative model of the stimulated muscles is desirable. The most commonly used model for isometric muscle has had a Hammerstein structure, in which a linear dynamic block is preceded by a static nonlinear function, To investigate the accuracy of the Hammerstein model, the responses to a pseudo-random binary sequence (PRBS) excitation of normal human plantarflexors, stimulated with surface electrodes, were used to identify a Hammerstein model but also four local models which describe the responses to small signals at different mean levels of activation. Comparison of the local models with the Linearized Hammerstein model showed that the Hammerstein model concealed a fivefold variation in the speed of response. Also, the small-signal gain of the Hammerstein model was in error by factors up to three. We conclude that, despite the past widespread use of the Hammerstein model, it is not an accurate representation of isometric muscle. On the other hand, local models, which are more accurate predictors, can be identified from the responses to short PRBS sequences. The utility of local models for controller design is discussed

Optimal control of ankle joint moment: Toward unsupported standing in paraplegia

This paper considers part of the problem of how to provide unsupported standing for paraplegics by feedback control. In this work our overall objective is to stabilize the subject by stimulation only of his ankle joints while the other joints are braced, Here, we investigate the problem of ankle joint moment control. The ankle plantarflexion muscles are first identified with pseudorandom binary sequence (PRBS) signals, periodic sinusoidal signals, and twitches. The muscle is modeled in Hammerstein form as a static recruitment nonlinearity followed by a linear transfer function. A linear-quadratic-Gaussian (LQG)-optimal controller design procedure for ankle joint moment was proposed based on the polynomial equation formulation, The approach was verified by experiments in the special Wobbler apparatus with a neurologically intact subject, and these experimental results are reported. The controller structure is formulated in such a way that there are only two scalar design parameters, each of which has a clear physical interpretation. This facilitates fast controller synthesis and tuning in the laboratory environment. Experimental results show the effects of the controller tuning parameters: the control weighting and the observer response time, which determine closed-loop properties. Using these two parameters the tradeoff between disturbance rejection and measurement noise sensitivity can be straightforwardly balanced while maintaining a desired speed of tracking. The experimentally measured reference tracking, disturbance rejection, and noise sensitivity are good and agree with theoretical expectations

Pre-testing of the WHO’s Educational Video: “How to Protect Yourself Against COVID-19”

The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was declared a public health emergency in many countries, including Indonesia. The World Health Organization (WHO) released an educational video, entitled "How to Protect Yourself Against COVID-19", which explained how to prevent the spread of COVID-19. This study is a qualitative study that aims to pre-test this video, based on the Information, Education, Communication (IEC) theory, by analyzing teenagers’ perceptions of the video. The design used was a Rapid Assessment Procedure (RAP), and the data were collected by conducting in-depth interviews with participants, through virtual meetings. The data were analyzed using a qualitative data matrix and thematic analysis. The results showed that all participants found the video regarding the prevention of COVID-19 spread to be attractive and comprehensible. In addition, the participants felt that the contents of the video were not contradictory to their personal values and that the message was targeted to everyone, including themselves. The video was also perceived to be persuasive. Overall, the participants held a generally positive perception of the video.

X-ray Crystallographic Characterization of the Co(II)-substituted Tris-bound Form of the Aminopeptidase from \u3cem\u3eAeromonas proteolytica\u3c/em\u3e

The X-ray crystal structure of the Co(II)-loaded form of the aminopeptidase from Aeromonas proteolytica ([CoCo(AAP)]) was solved to 2.2 Å resolution. [CoCo(AAP)] folds into an α/β globular domain with a twisted β-sheet hydrophobic core sandwiched between α-helices, identical to [ZnZn(AAP)]. Co(II) binding to AAP does not introduce any major conformational changes to the overall protein structure and the amino acid residues ligated to the dicobalt(II) cluster in [CoCo(AAP)] are the same as those in the native Zn(II)-loaded structure with only minor perturbations in bond lengths. The Co(II)–Co(II) distance is 3.3 Å. Tris(hydroxymethyl)aminomethane (Tris) coordinates to the dinuclear Co(II) active site of AAP with one of the Tris hydroxyl oxygen atoms (O4) forming a single oxygen atom bridge between the two Co(II) ions. This is the only Tris atom coordinated to the metals with Co1–O and Co2–O bonds distances of 2.2 and 1.9 Å, respectively. Each of the Co(II) ions resides in a distorted trigonal bipyramidal geometry. This important structure bridges the gap between previous structural and spectroscopic studies performed on AAP and is discussed in this context

Peranan K.H. Yahya Zainul Ma’arif dalam Pengembangan Tabligh di Pesantren: Studi Deskriptif Gerakan Tabligh di Pesantren Al-Bahjah Cirebon Jawa Barat

Setiap kyai atau muballigh itu menyampaikan pesan-pesan tabligh dengan jelas dan terang. Menyampaikan bukanlah dengan mengikut hawa nafsu saja akan tetapi menyampaikan tabligh itu sesuai dengan kebutuhan para masyarakat yang membutuhkan tabligh daripada seseorang kyai. Kyai sangat terkenal di pesantrennya dan kyai itu sering menjadi tempat rujukan buat para santrinya. Pondok Pesantren Al-Bahjah merupakan pesantren yang menitik beratkan tentang dakwah di dalam pesantren maupun di luar pesantren. Asal usul dan alasan kenapa dinamakan Al-Bahjah adalah karena lebih meninjau dari sisi makna yaitu makna cahaya atau kemilau sinar dengan harapan semoga pesantren ini bisa benar-benar menjadi penerang bagi umat Nabi Muhammad Saw. Tujuan penelitian ini adalah (1) peranan K.H. Yahya Zainul Ma’arif dalam pembinaan kader muballighin di Pesantren Al-Bahjah, (2) peranan K.H. Yahya Zainul Ma’arif dalam pengembangan tabligh melalui media di Pesantren Al-Bahjah, (3) bagaimana peranan K.H. Yahya Zainul Ma’arif dalam pengembangan tabligh di masyarakat. Dalam penelitian ini, peneliti menggunakan teori tabligh agar dapat memberikan informasi yang benar, pengetahuan yang faktual dan hakikat pasti yang bisa menolong atau membantu manusia untuk membentuk pendapat yang tepat dalam suatu kejadian atau dari berbagai kesulitan. Penelitian ini menggunakan metode deskriptif dan pendekatan kualitatif, yaitu dengan cara melalui pengamatan lapangan, wawancara, dan dokumentasi kepada Peranan K.H. Yahya Zainul Ma’arif dalam Pengembangan Tabligh di Pesantren Al-Bahjah. Hasil penelitian menunjukkan bahwa K.H. Yahya Zainul Ma’arif sangat berperan dalam pembinaan kader muballighin di pesantren. Dalam mencetak kader muballighin, K.H. Yahya Zainul Ma’arif sangat menegaskan kepada santrinya agar menjaga akhlak dengan baik supaya apabila terjun ke masyarakat dapat menjadi teladan yang baik. Selain itu, dalam usaha pengembangan tabligh, banyak media yang digunakan oleh K.H. Yahya Zainul Ma’arif antaranya dengan menggunakan radio, televisi dan facebook. K.H. Yahya Zainul Ma’arif adalah seorang kyai apabila menyampaikan pesan tabligh menggunakan metode yang penuh berhikmah dan buktinya adalah ramai audiens yang merasa senang dengan apa yang disampaikan. untuk mewarisi ilmu yang ada pada K.H. Yahya Zainul Ma’rif itu sendiri

Centre of pressure estimation during walking using only inertial-measurement units and end-to-end statistical modelling

Estimation of the centre of pressure (COP) is an important part of the gait analysis, for example, when evaluating the functional capacity of individuals affected by motor impairment. Inertial measurement units (IMUs) and force sensors are commonly used to measure gait characteristic of healthy and impaired subjects. We present a methodology for estimating the COP solely from raw gyroscope, accelerometer, and magnetometer data from IMUs using statistical modelling. We demonstrate the viability of the method using an example of two models: a linear model and a non-linear Long-Short-Term Memory (LSTM) neural network model. Models were trained on the COP ground truth data measured using an instrumented treadmill and achieved the average intra-subject root mean square (RMS) error between estimated and ground truth COP of 12.3mm and the average inter-subject RMS error of 23.7mm which is comparable or better than similar studies so far. We show that the calibration procedure in the instrumented treadmill can be as short as a couple of minutes without the decrease in our model performance. We also show that the magnetic component of the recorded IMU signal, which is most sensitive to environmental changes, can be safely dropped without a significant decrease in model performance. Finally, we show that the number of IMUs can be reduced to five without deterioration in the model performance.Comment: 21 page