High-speed Data Acquisition System Research Articles

First prototype of high-speed data acquisition system of ion source for neutral beam injection on EAST

The ion source is the critical part of Experimental Advanced Superconducting Tokamak (EAST) neutral beam injection (NBI) system. Two ion sources are equipped in one beam line. The voltage and current signals of grids are the important diagnostic data in the duration of beam extraction, especially the rising and sparking edge. In order to achieve the functions of data acquisition and isolation transmission, the first prototype of high-speed data acquisition system of ion source has been developed. The system contains the advantages of 40 MS/s sampling rate, 8-bits resolution and optical isolation transmission. Field programmable gate array (FPGA) is used as the control chip in the system. The system has been tested for the voltage of plasma grid (PG) and the beam current. The error range of system is <3% after the test. These results present that the data acquisition system is promising equipment for NBI.

Multichannel High-Speed Fiber Bragg Grating Interrogation System Utilizing a Field Programmable Gate Array

We demonstrate a multichannel high-speed fiber Bragg grating (FBG) interrogation system utilizing a field programmable gate array (FPGA). A temperature-controlled Fourier domain mode locking laser was operated with a sweep rate of 50.7kHz, sweep bands of 35nm, and an output power of 0.91mW. This laser enabled an FBG measurement speed of up to 9.9 s. Real-time processing could be achieved by incorporating a high-speed data acquisition system (DAQ) mounted on an analog to digital converter and an FPGA. The DAQ performed in-line processing with four 14-bit analog channels and a sampling frequency of 250MHz. The internals of the FPGA were implemented parallel processing for high-speed FBG detection to allow for the simultaneous measurement of the multiplexed FBG in three channels. We demonstrated that this system is capable of high-speed vibration measurements above several tens ofkHz with a multichannel.

The Design of High Speed Acquisition and Storage System Based on Labview

The design of high speed data acquisition and storage system is based on Labview. It can not only achieve high accuracy and high data rate but also use the software and hardware synchronization trigger to complete the multi-channel continuous real-time monitoring of the acquisition and storage periodic signal. Which is similar to the function of the oscilloscope. This system is based on high speed data acquisition card of NI company and Labview 2012 for PC software development platform. Data acquisition card is used to finish data acquisition of periodic signal through the serial port. It also collect data upload to upper computer. Upper computer collect data for storage display and analysis to realize the real-time monitor of multi-channel analog. The design of the sampling channel is 2, the sampling rate up to 200M/s, the sampling precision is 12 bits, and the sampling depth is 2000. Lots of verification prove that the design has good compatibility, performance and stability of the collection. Data error is negligible by analyzing the data collected. More importantly, the design can be as far as possible to restore the actual signal source data without distortion. This paper provides a portable design for high speed data acquisition, which can be widely applied in the engineering of modern test and measurement technology.

Pulse profile and metal transfer in pulsed gas metal arc welding: droplet formation, detachment and velocity

ABSTRACTThe influence of current profile and pulse parameters on droplet formation and transfer was investigated. One profile has an exponential ramp up and down in the current pulse shape, while the second is nearly square shaped. High-speed photography, synchronised with a high-speed data acquisition system, was used to monitor the droplet formation and transfer. It was found that for long-tail current profile, most of droplet formation and detachment occurs before background current is reached. While, for the nearly square pulse, most of droplet formation and transfer occurs during background current, giving a stable and smooth metal transfer. The arc attachment position was found to vary for the different profiles. Droplet speed was measured, and it was found that it is proportional to the peak current and inversely proportional to background current. Dimensionless process parameters were defined and used to predict droplet speed using a neural networks algorithm.

40 Gbps data acquisition system for NectarCAM

The Cherenkov Telescope Array (CTA) will be the next generation ground-based gamma-ray observatory. It will be made up of approximately 100 telescopes of three different sizes, from 4 to 23 meters in diameter. The previously presented prototype of a high speed data acquisition (DAQ) system for CTA (CHEP 2012, [6]) has become concrete within the NectarCAM project, one of the most challenging camera projects with very demanding needs for bandwidth of data handling. We designed a Linux-PC system able to concentrate and process without packet loss the 40 Gb/s average data rate coming from the 265 Front End Boards (FEB) through Gigabit Ethernet links, and to reduce data to fit the two ten-Gigabit Ethernet downstream links by external trigger decisions as well as custom tailored compression algorithms. Within the given constraints, we implemented de-randomisation of the event fragments received as relatively small UDP packets emitted by the FEB, using off-the-shelf equipment as required by the project and for an operation period of at least 30 years. We tested out-of-the-box interfaces and used original techniques to cope with these requirements, and set up a test bench with hundreds of synchronous Gigabit links in order to validate and tune the acquisition chain including downstream data logging based on zeroMQ and Google ProtocolBuffers [8].

Predicting the Grounding Topology Based on Grounding Impedance and the Pattern Recognition Framework: A Case Study on One to Four Ground Rods in Straight Line

This paper presents a system which predicts the grounding topologies of grounding systems (GS) with one, two, three, or four ground rods in straight line, when no prior information about the grounding topology, soil or rod properties is given. This is achieved through the exploration of the information contained into the impulse response of the GS together with the pattern recognition framework. The proposed system is composed by four main elements, an excitation system, a high-speed data acquisition system, a feature extraction, and a pattern recognition model. Experimental setup comprises the evaluation of the accuracy of the proposed system in discriminating among four grounding configurations, composed by the topologies of one, two, three, and four ground rods in straight line. This paper also proposes a new data driven approach to improve the classification performance, in pattern classification models, when dealing with undersampling problem in the acquired signal used to extract the features.

IMPROVEMENT OF TRADITIONAL ESR PERFORMANCE FOR RAPID DETECTION OF FREE RADICALS IN MATERIALS

To detect the presence of free radicals in materials, a traditional Electron Spin Resonance (ESR) requires repeating setting values of the external magnetic field ( B 0 ) as well as the frequency of microwave signal ( u ) to achieve resonance conditions, and it must be conducted manually. The procedure requires considerable time, so that become ineffective. In this paper, we propose a simple technique to improve the functionality of the traditional ESR by implementation of ramp-type magnetic field and high-speed data acquisition system. In here, we generate ramp-type voltage signal based on PIC16F876 microcontroller as the main device. This signal is converted to the current source by using the circuit of V to I converter, then injected to the Helmholtz coil to generate a ramp-type magnetic field. Some experiments are carried out in order to make validation and determine the performance of the developed system. By the technique, the traditional ESR becomes an automatic ESR-spectrometer and has the capability to identify some kinds of free radicals faster. Keywords: ESR , free-radical , ramp-B .

Performance study of optical sensor for parameterization of staple yarn

This work deals with the development of a low cost high resolution yarn characterization unit with optical sensor. The developed system can measure yarn average diameter, diameter variation over length, variation of yarn mass, yarn faults, number of hairs at specific distances from yarn core, mean absolute deviation and coefficient of variation in a single run. The most lucrative feature of the newly developed instrument is one hundredth times lower cost and 8 times higher resolution than the existing one. The sensor signal is fed to a high speed data acquisition system and custom made software to get yarn parameters when the yarn is passed in front of the sensor by mechanical setup. The output of the system is compared with the output of the widely used Tester for the said purpose. Moreover, unlike the standard tester, the newly developed instrument is able to furnish absolute mass and diameter of the yarn in real unit. These important parameters certainly give two important estimates for judging the final look of the fabric. The repeatability of results is insignificant in 0.5% level. Calibration is done by taking a standard wire. Jute and cotton yarns of different tex values are tested with the instrument and results are reported. FFT is also performed to provide equivalent frequency response of diameter/mass profile. It seems to be more significant representation of the parameters under consideration.

Design of Digital Acquisition Circuit for Inertial Sensor Based on FPGA

In order to realize high-speed analog sampling and noise analysis, the paper put forward a design scheme of the high-speed data acquisition and analysis system based on FPGA, the system uses Cyclone series FPGA with high-speed A/D converter, and using fast Fourier analysis core of the Altera Company. The ADC model is AD9643 chip. The test results show that the prototype can simultaneously collect three output signals, and real-time processing to the host computer display. The measured gyro resonance frequency is stable at 324.88 kHz, fluctuation range is 9Hz, and the mean square deviation of the peak value is 0.008 V on the output voltage of reference point. The detection system is stable and has high precision. The digital detection circuit can be applied to the signal processing of MEMS gyroscope, which can improve the stability and anti-jamming of MEMS gyroscope.

Fluid Imbibition-Coulped Laser Interferometry As a Tool for Optical Biosensing with Anodic Aluminum Oxide

Optofluidics is a technology based on the fusion between microfluidics and optics. It is related to a variety of phenomena in which an interaction between light and fluids is found. It can be applied to the control of fluid properties by light, to the design of variable geometry optical elements by means of the adaptability of the fluid or by using optics to interrogate fluid properties. On the other hand, anodic aluminum oxide (AAO) is a porous material obtained by the electrochemical anodization of aluminum with a growing interest in nanotechnology because of its cost-effective production process and its promising variety of applications[1]. Recently, we have introduced an optofluidic technique called fluid imbibition-coupled laser interferometry (FICLI), based on the study by optical means of the liquid infiltration dynamics into AAO. We demonstrated its high accuracy for the characterization of the material[2,3]. In this work, we explore the possibilities of using such a sensitive technique as a sensor of biological species. Fluid imbibition-coupled laser interferometry consists of the measurement of the capillary filling dynamics of a fluid into the AAO nanopores. Such measurement is performed by monitoring light intensity interferometric fluctuations of a laser beam in real-time as the liquid infiltrates the pores. An illustration of the measurement system can be seen in the figure. AAO membranes with 50 µm-long pores are used (see SEM pictures in the figure) and the laser beam is reflected at its top and bottom interfaces creating a time-resolved intereference. Light intensity fluctuations are measured by a photodetector and a high-speed data acquisition system, and are analyzed on the basis of mathematical models of the filling kinetics. This technique has shown enough accuracy to demonstrate that AAO nanopores are actually conical with an angle as small as 0.007º. The processing of the time-resolved interferograms, as the one shown in the figure, can be done in several ways. The simplest method consists of measuring the filling time of the pores from each side of the membrane and combine these measurements with the information about the fluid and the surface properties (viscosity, surface tension, contact angle) to obtain the values of the radius at each pore end. A more elaborate method permits the determination of the pore profile by the inversion of the filling dynamics integral equations provided accurate measurement of the time-resolved interferograms for the filling from each end of the pores are obtained. In this work we introduce an alternative method based on the discretization of the filling dynamics equations, what permits to obtain a direct and accurate determination of the average radius of the nanopores. In order to evaluate the accuracy of this alternative method we applied different modifications to the pore geometry and we measured the pore radius modification by the different methods. Pore radius increase was achieved by applying controlled wet etching to the as-produced AOO membranes with increasing time. On the other hand, pore radius decrease was achieved by depositing successive bilayers of polyelectrolytes. Results show that the proposed technique is accurate enough to sense pore radius variations as small as 4 nm, in the range of the size of many biological macromoleclues such as proteins, antibodies or aptamers. With this ability in mind, we have studied the application of the technique to sense such biological species. In this communication we will report our results on the measurement of the changes in the filling dynamics of AAO membranes after the functionalization of their surface and the attachment of the different molecules: i) proteins like bovine serum albumin (BSA), ii) the successive attachment of the IgG-aIgG antibody-antigen pair with a view to the application of the technique as an immunosensor and iii) the attachment of an aptamer and the detection of changes in their conformation.

An FPGA-Based High-Speed Error Resilient Data Aggregation and Control for High Energy Physics Experiment

Due to the dramatic increase of data volume in modern high energy physics (HEP) experiments, a robust high-speed data acquisition (DAQ) system is very much needed to gather the data generated during different nuclear interactions. As the DAQ works under harsh radiation environment, there is a fair chance of data corruption due to various energetic particles like alpha, beta, or neutron. Hence, a major challenge in the development of DAQ in the HEP experiment is to establish an error resilient communication system between front-end sensors or detectors and back-end data processing computing nodes. Here, we have implemented the DAQ using field-programmable gate array (FPGA) due to some of its inherent advantages over the application-specific integrated circuit. A novel orthogonal concatenated code and cyclic redundancy check (CRC) have been used to mitigate the effects of data corruption in the user data. Scrubbing with a 32-b CRC has been used against error in the configuration memory of FPGA. Data from front-end sensors will reach to the back-end processing nodes through multiple stages that may add an uncertain amount of delay to the different data packets. We have also proposed a novel memory management algorithm that helps to process the data at the back-end computing nodes removing the added path delays. To the best of our knowledge, the proposed FPGA-based DAQ utilizing optical link with channel coding and efficient memory management modules can be considered as first of its kind. Performance estimation of the implemented DAQ system is done based on resource utilization, bit error rate, efficiency, and robustness to radiation.

A real-time online data acquisition system for Dragon-I linear induction accelerator

An extensible high-speed accelerator data acquisition system (ADAS) for the Dragon-I linear induction accelerator has been developed. It comprises a VXI crate, a controller, four data acquisition plug-ins, and a host computer. A digital compensation algorithm is used to compensate for the distortion of high-speed signals arising from long-distance transmission. Compared with the traditional oscilloscope wall, ADAS has significant improvements in system integration, automation, and reliability. It achieves unified management of data acquisition and waveform monitoring and performs excellently with a 107-ps high-accuracy trigger and 32-channel signal monitoring. In this paper, we focus on the system architecture and hardware design of the ADAS, realization of the trigger, and digital compensation algorithm.

Free-surface air entrainment in open-channel flows

In hydraulic engineering, free-surface aeration is a natural phenomenon occurring in smooth channel flows. In self-aerated flows, a key aspect that has not yet been well understood is the formation mechanism of free-surface air entrainment. In this research, the process of free-surface entrapped deformation is analyzed theoretically and the critical radius of curvature for air entrainment is obtained, affected by flow mean velocity and depth. When the severity of local free-surface deformation exceeds the critical condition, the entrapped free surface encounters closure in the unstable deformation movement process, resulting in air entrainment. This inference agrees well with observed experimental results that are obtained from the processes of surface entrapped deformation and air entrainment captured by a high-speed camera-based data acquisition system. This agreement indicates that self-aeration occurs in low-velocity open-channel flows. It is also confirmed that free-surface turbulent deformation provides a mechanism for air entrainment.

STM32 프로세서를 이용한 고속 데이터 수집 및 융합 시스템 설계

In this paper, we describe the design of a high speed data acquisition system(DAS) with STM32 processor based on Cortex-M4. The system is used for the sensor devices to collect raw data on production lines at factory and send them to the servo computer in real time. The system is designed for multi functions with universal asynchronous receiver and transmitter(UART), analog to digital converter(ADC), digital to analog converter(DAC), and general purpose input output(GPIO). those are well tested for various data acquisition and high speed motor control in real time.

基于Labview的高速数据采集与存储系统的设计

针对市面上现有的一般的数据采集卡采样位数不高和采样内存不够，从而不能进行长时间对信号进行有效的连续采样等问题。本文设计了基于labview的高速数据采集和存储系统。该系统能够实现高精度、高数据率，还可以采用软件和硬件同步触发的方式来完成对周期信号进行多通道连续实时监测采集和存储，使数据采集存储系统的采样内存扩展至电脑的内存。本系统以NI公司的高速数据采集卡为基础，以labview 2012为上位机软件开发平台，由数据采集卡对周期信号进行数据采集再通过串口将采集到的数据上传到上位机，上位机对采集的数据进行存储、显示和分析实现了多通道模拟量的实时监测。该设计最终实现了采样通道数为2，采样速率为200 M/s，采样精度为12位，采样深度达到2000。平台有效性验证了该采集平台兼容性好、性能稳定采集信号误差小，能够尽量做到对实际信号源数据的无失真还原。本文为高速数据采集提供了一种便携的设计方案，可以广泛的应用到现代测试测量技术工程中。 In view of the existing general data acquisition card in the market, it is not enough to have high sampling and sampling memory, so that the acquisition system cannot be carried out for a long time. The design of high speed data acquisition and storage system is based on Labview. It can not only achieve high accuracy and high data rate but also use the software and hardware synchronization trigger to complete the multi-channel continuous real-time monitoring of the acquisition and storage of periodic signal which is similar to the function of the oscilloscope. This system is based on high speed data acquisition card of NI company and Labview 2012 for PC software development platform. Data acquisition card is used for data acquisition of periodic signal through the serial port and collect data upload to upper computer. Upper computer collects data for storage, display and analysis to realize the real-time monitoring of mul-ti-channel analog. The design of the sampling channel is 2, the sampling rate up to 200 M/s, the sampling precision is 12, and the sampling depth is 2000. Platform validation of the collection platform has good compatibility, performance and stability of the collection signal error is ignorable, which can be as far as possible to the actual signal source data without distortion reduction. This paper provides a portable design for high speed data acquisition, which can be widely used in the engineering of modern test and measurement technology.

Cone crusher modelling and simulation using DEM

Compressive crushing has been proven to be one of the most energy efficient principles for breaking rock particles (Schönert, 1979). In this paper the cone crusher, which utilizes this mechanism, is investigated using the discrete element method (DEM) and industrial scale experiments. The purpose of the work is to develop a virtual simulation environment that can be used to gain fundamental understanding regarding internal processes and operational responses. A virtual crushing platform can not only be used for understanding but also for development of new crushers and for optimisation purposes.Rock particles are modelled using the bonded particle model (BPM) and laboratory single particle breakage tests have been used for calibration. The industrial scale experiments have been conducted on a Svedala H6000 cone crusher operated as a secondary crushing stage. Two different close side settings have been included in the analysis and a high speed data acquisition system has been developed and used to sample control signals such as pressure and power draw in order to enable detailed comparison with simulation results. The crusher has been simulated as a quarter section with a batch of breakable feed particles large enough to achieve a short moment of steady state operation. Novel methods have been developed to estimate the product particle size distribution using cluster size image analysis. The results show a relatively good correspondence between simulated and experimental data, however further work would be need to identify and target the sources of observed variation and discrepancy between the experiments and simulations.

An Update of Spacecraft Charging Research in India: Spacecraft Plasma Interaction Experiments—SPIX–II

Arcing on spacecraft solar panels has been a major challenge since it was first observed in late 1970s. Scientists of leading scientific countries like USA, Japan, France, and others are working hard to understand various aspects of this charging-arcing phenomenon. Based upon the experimental simulation results, a few arc mitigation techniques have been developed. In 2003, the Indian Space Research Organization (ISRO) realized the necessity to develop an experimental setup for understanding the charging-arcing phenomenon on satellite's solar panels when parked in lower earth orbit (LEO) in the Space Plasma Interaction Experiments (SPIX) facility. The SPIX facility was jointly developed as a collaborative research project between the ISRO and the Institute for Plasma Research. In 2010, an initiative was taken for the upgradation of the SPIX facility for testing both LEO and geosynchronous earth orbit (GEO) satellite's solar panels by the following standard ISO 11221 experimental procedure and indigenously developed high-speed data acquisition and analysis system. Various types of solar panel coupons were tested in upgraded SPIX-II facility. Sample solar panel coupons used in the experiments can be categorized based on the types of solar cells and the configurations of solar cell that includes different interstring gaps and grouting. For LEO satellite coupons, depending upon the types of solar panel coupons, different bias voltages were applied and threshold voltage was determined. Threshold arc tests were done at different bias voltages and electron gun energies for GEO satellite's coupons. Arc rates and threshold voltages were measured for each type of solar panel coupon, which determined their durability and reliability in harsh environmental conditions. Grouted solar panel coupons had higher threshold voltage in both LEO and GEO worst environmental conditions. Results showed good repeatability and reproducibility for both LEO and GEO experiments. To measure sustained arc conditions, experiments were performed with different string voltages and string currents in both LEO and GEO environmental conditions. It was experimentally validated that the probability of temporary sustained arc or permanently sustained arc increases on increasing either string voltage or string current. In addition, an attempt is also made to understand the role of plasma curing of solar panel coupons and its impact on arc mitigation for GEO environment like space conditions.

Machinability of lithium disilicate glass ceramic in in vitro dental diamond bur adjusting process

Esthetic high-strength lithium disilicate glass ceramics (LDGC) are used for monolithic crowns and bridges produced in dental CAD/CAM and oral adjusting processes, which machinability affects the restorative quality. A machinability study has been made in the simulated oral clinical machining of LDGC with a dental handpiece and diamond burs, regarding the diamond tool wear and chip control, machining forces and energy, surface finish and integrity. Machining forces, speeds and energy in in vitro dental adjusting of LDGC were measured by a high-speed data acquisition and force sensor system. Machined LDGC surfaces were assessed using three-dimensional non-contact chromatic confocal optical profilometry and scanning electron microscopy (SEM). Diamond bur morphology and LDGC chip shapes were also examined using SEM. Minimum tool wear but significant LDGC chip accumulations were found. Machining forces and energy significantly depended on machining conditions (p<0.05) and were significantly higher than other glass ceramics (p<0.05). Machining speeds dropped more rapidly with increased removal rates than other glass ceramics (p<0.05). Two material machinability indices associated with the hardness, Young’s modulus and fracture toughness were derived based on the normal force-removal rate relations, which ranked LDGC the most difficult to machine among glass ceramics. Surface roughness for machined LDGC was comparable for other glass ceramics. The removal mechanisms of LDGC were dominated by penetration-induced brittle fracture and shear-induced plastic deformation. Unlike most other glass ceramics, distinct intergranular and transgranular fractures of lithium disilicate crystals were found in LDGC. This research provides the fundamental data for dental clinicians on the machinability of LDGC in intraoral adjustments.

Data Acquisition and Processing Method Adequate for High Speed Transient Electrical Events

Many programmable electronic modules for data acquisition and processing can be found in power systems. To monitor and record different specific high speed transient events in energetic systems, an adequate data acquisition and processing method is required. This paper deals with such method and its application in data acquisition for implementation of complex protection functions. The acquisition routine for analog and digital channels, detailed acquisition and storing process for analog and digital values, storing and calculation method for acquired digital and analog values are all presented. The proposed method is adequate for many and various practical applications which require high speed data acquisition systems.

Peak Force Measurements for a Combustion-Driven, Direct-Conversion, Actuation System for Powered Orthoses1

As fabrication processes improve, and portable power sources are scaled down, the more feasible it becomes to produce untethered powered orthoses, prostheses, and exoskeletons for human assistance. The advent of more-energy-dense batteries, such as lithium ion, has spurred the research, development, and commercialization of a number of electrically driven active orthoses, including direct motor drives [1], electrohydraulics, and “smart-material” actuators [2]. Advances in manufacturing have also made pneumatically driven actuators more lightweight through component integration [3]. Figure 1, however, illustrates the challenge in developing effective mobile assistive orthoses and prostheses—to operate for more than a few minutes, the requisite power-source mass must increase. For an hour, or more, of operation, electroactive polymers are shown to have the best mass-to-power ratio, with solenoids being a distant second (roughly 1 order of magnitude difference, but closing).Reproducing the plantarflexion (step-off) function of a healthy ankle joint is particularly challenging as well. A significant power spike must be generated within, roughly, 100 ms, and it must dissipate just as quickly (Fig. 2). Precisely metered and timed fuel combustion within an actuator can provide the requisite torque and power peaks. Also, the specific energy of hydrocarbon fuels is more than 1 order of magnitude higher than the best batteries, affording much lighter-weight actuation systems and far greater operation times for a given mass of energy storage [6].Figure 3 shows a conceptual model of an ankle-foot orthosis that employs combustion to directly provide plantarflexion actuation from fuel combustion [6]. This particular design also employs energy-recovery to provide the dorsiflexion (toe-up) actuation as well. At a theoretical thermodynamic efficiency of &gt;60%, very little thermal energy will be wasted (∼7 W), requiring minimal passive heat dissipation to maintain a surface-contact temperature of &lt;41 °C. Carbon dioxide and water vapor are the predominant exhaust products, produced only when walking, at amounts that pose a minimal asphyxiation hazard if operated in a closed environment.Certainly, before building such a system, characterization of the combustion pressures over time, and extension rates of the piston under load, is critical. A test stand was constructed to experimentally determine the forces that can be generated through combustion of various fuel types (Fig. 4). To date, propane (C3H8) and hydrogen have been tested. Propane is a readily available fuel, used frequently in gas grills and fleet vehicles, with a specific energy (lower heating value) of 46 MJ/kg. Hydrogen can be produced inexpensively via electrolysis, but with a specific energy of 120 MJ/kg (∼3 x propane) and explosive limits between 4% and 75%, care must be taken.Due to the near-instantaneous release of chemical potential energy in the combustion process, accurately measuring the forces generated on a piston is a challenge. Maximal pressures and forces are required to calculate initial sizes for components of the actuation system. For expediency, to collect the requisite data without a high-speed data-acquisition system and sensors—until funds are available, it was decided that the crushing of small, high-tolerance (±1%) copper spheres would provide this measure of maximal force generated by the piston. The spheres were positioned inside a shaft coupling between the combustion-driven-piston shaft and the shaft of a loading piston. Static crushing of 1.98 mm-diameter copper spheres, using the loading piston and an attached, calibrated load cell, provided a reference curve (Fig. 5). The load cell’s gauge has only a 200 Hz sampling rate; so it cannot reliably capture the peak forces during combustion. Plastic deformation of the spheres accurately records the peak forces experienced, through interpolation from the reference curve. Extrapolation also provides an estimate of peak forces beyond the reference curve.Figure 5 shows the results of these preliminary tests. Each trial used 26 ml of a 50/50 mix of hydrogen and air. Three combustion trials used 2.07 bar compression pressure, and the other three used 2.76 bar. Variability in metering the air and hydrogen, as well as in setting the compression pressure, resulted in the spread of the data points. These will need to be better controlled for higher accuracy, and more static tests are required toward the limit of the load cell, so that extrapolation is not necessary.Peak forces greater than 1.8 kN (400 lbf) were achieved in these preliminary trials, enough to provide the requisite 75 N m peak torque with just a 4.2 cm-radius pulley. A pneumatic loading cylinder was used in these trials to limit the peak forces. The orthosis will also employ compliance, e.g., springs, to control these peaks, beyond that provided by fuel and air metering. A hydraulic loading cylinder, or shaft lock on the pneumatic one, will be used to approach a measurement of absolute peak forces attainable.