Acceleration Switch Research Articles

Anti-sway control of variable rope length container crane based on phase plane trajectory planning

An overhead crane system is a complex time-varying system if it includes simultaneous hoisting and moving operations. To address the problem that time-varying systems usually have no exact analytical solution, an anti-swing method based on linear approximation of the phase plane trajectory is proposed. Specifically, the phase plane trajectory of the swing angle is first analyzed and it is found that the double-step acceleration method with unequal acceleration amplitude and acceleration time has a combination of limit loops in the phase plane trajectory of the swing angle when the rope length varies, so the average rope length of each section is used to approximate the natural oscillation frequency. Next, the input shaping technique is used to shape the input signal into the desired output signal so that the load swing angle can follow the planned trajectory. The desired acceleration amplitude and switching time are then derived based on the geometric relationship between the swing angle in the phase plane and the specific physical constraints. Finally, the feasibility of the proposed method is verified by numerical simulations.

Low-G Triggered Acceleration Switch for Near-Zero Power Wake-Up Application.

A low-g triggered micro-electromechanical system (MEMS) resonant acceleration switch is designed, fabricated and tested in this paper for near-zero power wake-up applications. The switch is actuated by ambient low-g vibration, consuming zero power while waiting for vibration at its resonant frequency. A cantilever beam and proof mass structure is adopted in the switch. The patterns of spiral cantilever beams are designed for low resonant frequency and threshold. Once the vibration with resonant frequency exceeds the acceleration threshold of the switch, the movable electrode becomes sufficiently displaced to contact the fixed electrodes and causes them to trigger. The dynamic responses of the switch are tested on a piezoelectric stack. The experimental results show that the switch closes under vibration at a frequency as low as 39.3 Hz and at an acceleration threshold of 0.074 g. A wake-up sensor node connected to the switch can awaken when the switch is under vibration as an intended characteristics.

Secure Data Sequence Recognition of All-Optical High-Speed Network Using Semiconductor Optical Amplifier

Semiconductor optical amplifier (SOA) has nonlinear optical effect and integration advantages, and is widely used in all-optical logic gates. Hence, it is used in the identification of all-optical high-speed network security data sequences. First, the SOA model is established and then simplified based on the existing model. On this basis, the identification model of all-optical high-speed network security data sequence is established, and the concept of integrated turbo-switch is introduced. The structure of the turbo-switch is analyzed. Then, an integrated turbo-switch architecture based on SOA-Mach Zehnder interferometer (MZI) is proposed, and its performance is verified by simulation. A data sequence recognition method for all-optical high-speed network security is proposed based on the integrated acceleration switch, and the difficulty of result recognition is analyzed. The simulation results of integrated turbo-switch show that when 1550 nm light passes through MZI, the interference can be almost completely cancelled, and the corresponding phase difference of 1538 nm light is less than 3 radians, that is, some light can pass through MZI. After the bias current of SOA of upper and lower arms of SOA-MZI is properly adjusted, MZI can play the function of tunable filter. Adjusting the bias current of SOA1 and SOA2 in the turbo-switch can control the “overshoot” program in the gain recovery curve, make SOA2 in a saturated working state, optimize the gain recovery curve, and improve the SOArelated mode effect, so that the turbo-switch can also output a more stable waveform under continuous “1” input. The recognition difficulty test shows that the target sequence after the cycle and the data sequence to be recognized are used for the “Exclusive NOR” operation, and the “AND gate” is added to realize the data sequence recognition and reduce the recognition difficulty.

DC-link current based position estimation and speed sensorless control of a BLDC motor used for electric vehicle applications

Abstract Sensors of any kind contribute to extra space and electronics when they are used in any application. Besides, the sensor noise also has the effect of altering the overall gain of the system. This is more prevalent in non-linear systems like motor control. In applications which have strict space constraints like Electric vehicles, the use of sensors must be optimized, which, in turn, gave rise to many sensorless state estimation strategies. This paper proposes a novel sensorless control technique for brushless direct current (BLDC) motor used in electric vehicle applications. The concept of sensorless control in BLDC Motor drive eliminates the hall-effect position sensor, thereby giving better performance and improves the robustness of the overall drive system. The main objective of this work is to estimate the position of the motor at standstill condition using stator saturation effect concerning the rotor, accelerate the motor from standstill so that enough back EMF is generated. This acceleration technique speeds up the motor to a stage where a self-actuating control mechanism is used to generate control signals with back EMF or line voltages. The motor can be started with a load, which is a significant constraint for electric vehicle application. The proposed method will avoid the reverse rotation of the motor. The proposed work is simulated in Matlab/Simulink software, and results obtained show that it works well under dynamic conditions of starting, acceleration and load switching. The hardware setup of the proposed work is developed using the TMS320F2812 DSP processor. Simulation and experimental results validate the effectiveness of the proposed work for electric vehicle application.

A parametric analysis based design framework for MEMS g-switch accelerometers

We present an experimentally verified novel design framework for MEMS g-switch acceleration switches. These switches need to engage a physical latch upon sensing a specified threshold acceleration. It is this physical contact between two surfaces under dynamic conditions that introduces nonlinearity in the system response and makes the task of design optimization difficult. We first find analytical solutions for displacement and velocity of the proof mass by linearizing the friction term using a single degree of freedom model and representing the acceleration profile by a Fourier series. We then use these solutions, along with latching constraints on them, to study how the lumped design parameters – mass, suspension spring stiffness, and latching spring stiffness – vary with increasing threshold acceleration. The latching constraints ensure that latching does not occur for any magnitude of acceleration less than the specified threshold value. Subsequently, we build a g-switch model in SIMULINK that uses the variation in design parameters for a given acceleration profile to find an optimal set of values of design parameters for a specified threshold acceleration. We verify our model by fabricating a latch accelerometer using the parameters obtained from this model for a 60g threshold acceleration. A shock input of 60g magnitude and 1.2 ms pulse width is given to the fabricated acceleration switch and the experimental response is recorded using high-speed video images. The analytical response and the experimental response show good agreement. Hence, we believe that this novel design framework can be used to fabricate a latch accelerometer for any arbitrary input shock profile.

An 8-Bit Digitally Operated Micromachined Accelerometer

This work presents successful implementation and characterization of an 8-bit digitally operated micromachined accelerometer. Such device is comprised of an electrostatically tunable acceleration switch with 8 sets of electrostatic tuning electrodes. Similar to bits in a binary number, the tuning force of each electrode set increases by a factor of 2 with respect to the adjacent electrode set. A fabricated device has been interfaced with a micro-controller performing a binary search by controlling state of different tuning electrodes (ON or OFF) to interpret the acceleration with 8 bits of resolution. Measurement results show good agreement between the applied acceleration and the binary acceleration output of the sensor reported by the controller. The tested 8-bit prototype has full-scale acceleration of 2.7g with resolution 10.5 mg s (1/28 of full scale). Requiring only a bias voltage for operation (zero static current) and readout of the switch output (a digital high or low voltage) that can be performed directly by a digital controller, such devices can lead to ultra-low power accelerometers by eliminating the need for an analog-front-end. [2020-0201]

Response analysis of MEMS based high-g acceleration threshold switch under mechanical shock

Failures of MEMS devices under shock are due to the overlap of the static and moving parts. The shock response of the microstructure under mechanical shock is investigated in this paper. This work presents modelling and simulation of the microstructures such as microcantilever, fixed–fixed flexure and serpentine structure and is further extended to optimize the response of high-g acceleration threshold switch under mechanical shock. The latching threshold for the high-g acceleration switch is estimated using the geometrical structure. The natural frequency of the serpentine spring-mass structure is selected to achieve the required displacement for latching. The dimensions of the switch are optimized in accordance with the natural frequency and to meet the requirement of latching for a given shock. The switch is fabricated on silicon on insulator wafer with a deep reactive ion etching process. The switch is tested on the static mechanical shock of 3500 g and shows a good agreement between analytical, numerical and experimental results.

A Bisection Algorithm for Time-Optimal Trajectory Planning Along Fully Specified Paths

The time-optimal trajectory planning problem involves minimizing the time required to follow a path defined in space, subject to kinematic and dynamic constraints. Here, we introduce a novel technique, called the bisection algorithm (BA), which is fully implemented in C++ and extends dynamic programming approaches to the problem. These approaches, which rely on dividing the global problem into a series of simpler subproblems, become increasingly advantageous compared to direct transcription methods as the number of problem constraints increases. In contrast to nearly all other dynamic programming approaches, BA does not rely on finding a maximum-velocity curve or explicitly finding acceleration switching points during the trajectory planning process. Additionally, only one forward and one backward integration are used, during which all constraints are imposed. This approach is made feasible through careful control of the numerical integration process and the use of a bisection algorithm to resolve constraint violations during integration. BA is shown to be significantly simpler, faster, and more robust than recently proposed algorithms: a direct comparison is made for a series of paths to be followed by a serial manipulator, subject to kinematic constraints. The wide applicability of BA is then established by solving the time-optimal problem for a parallel manipulator following a complex path, subject to both kinematic and dynamic constraints.

Research on flexible control algorithm for acceleration/deceleration in heavy-duty motion

An algorithm for acceleration/deceleration control is proposed in this paper to improve the flexibility of the heavy-duty motion system. The algorithm is based on the five-segment S-type acceleration/deceleration curve. During the acceleration switching time, a circular arc is used to smooth the curve, and the running time of each stage could be reasonably allocated by cyclic iteration. A parameter is defined to quantify the degree of flexibility of the acceleration/deceleration process to match the actual project. This paper will build the model to compare the good and bad point of different algorithms. The result shows that the vibration and impact during the acceleration and deceleration process can be effectively reduced, which means that the flexibility of the system has been greatly improved.

Novel Approach of Implementing Effortless Manoeuvrability in Vehicle for Physically Challenged

Automobile is a comprehensive invention which became a basic need for every human. But some modifications were necessary in automobile design in case of differently abled person. The existing vehicle comprises with usual hand twist acceleration, hand lever braking and handlebar steer control. Conventionally, three wheeled rear axles are used by physically challenged person. If the physically challenged person is about to park his/her vehicle then he/she should get down for moving the vehicle. Hence a reverse drive feature is proposed for vehicle which can help them to move in reverse direction when they are in seating position. In our proposed vehicle, the acceleration can be controlled either by right hand twist accelerator in handlebar or by foot pedal. The acceleration switch determines the working of accelerators. For left hand impairment, they can switch to foot pedal acceleration. Here the rear braking is applied by left hand brake lever or foot brake pedal (to apply rear brake if they are left hand impaired).

Low-Power Resonant Acceleration Switch for Unattended Sensor Wake-Up

We have designed, built, and tested novel low-power (less than 10 nW) resonant acceleration switches. The switches respond to vibration at specifically designed frequencies between 30 and 1000 Hz by resonating with sufficient displacement to close an electrical contact and consume power only while vibration is occurring. A rotational design avoids switch closings from DC acceleration, and the quality factor, adjustable between 102 and 105 by tuning the vacuum level, sets the resonant detection threshold. The design includes electrostatic combs for self-test and frequency tuning (up to several Hz), compliant contacts to reduce squegging and contact damage, and ruthenium-coated contacts for improved reliability. Fabrication is accomplished with deep reactive ion etching at up to 50:1 aspect ratios, HF vapor release, and XeF2 frequency trimming (up to 30% of the as-fabricated frequency). Testing with vibration recordings played back through a shaker table demonstrates that the switches correctly identify a target without any false alarms. [2018-0061]

Design of Multi-threshold Acceleration Switch Based on Matlab

Acceleration switch can trigger switches according to the variation of external acceleration without complex control system and circuit. With the excellent characteristics of integration of sensor and actuator, zero power consumption and high reliability, multi-threshold acceleration switch has great application value in the fields of vehicle safety, aerospace and industrial equipment. In order to reduce the complexity of the measurement system and improve the reliability, we realized the design of a multi-threshold and anti-overloading acceleration switch which can distinguish specific pulse width. Additionally, the magnetic elastic contact is designed to prevent the rebound phenomenon when switch is overloaded. Considering the coupling force of spring, magnetic elastic contact and magnetic, we built the dynamic model and analysed the influence of the acceleration threshold and the pulse width on the switch actuation. The numerical simulation shows that the proposed switch has accurate sensitivity of acceleration excitation with specific threshold and certain pulse width, and it also has the ability of anti-overload. Consequently, the proposed method provides a new method for designing acceleration switch.

Sensitivity-Based Reliability Analysis of MEMS Acceleration Switch

MEMS acceleration switches have been used in many engineering applications. In this paper, the reliability of MEMS switch is evaluated under various uncertainties from materials and manufacturing process. First, the performance of MEMS switch is modeled using 1D mass-spring-damper-contact system. Different from conventional lumped element methods, the model includes the effect of geometric parameters as well as contact conditions. The parameters of 1D models are calibrated using a high-fidelity finite element model. For reliability assessment, four different methods are used in order to compare computational cost as well as accuracy in predicting reliability. It turned out that sensitivity-based reliability method has several benefits, such as computational time and identifying important parameters that contribute significantly to reliability. The sensitivity analysis showed that the cross-sectional height and the length of folded-beam contribute most significantly to the reliability of switch-on condition. After changing the length of the beam, the probability of failure was improved from 0.168 to 0.0003.

Design and fabrication of a silicon-based MEMS acceleration switch working lower than 10 g

This paper reports a low-g MEMS acceleration switch with threshold acceleration below 10 g. The proposed switch is made of single-crystalline silicon for high thermal stability and stress-free structure. A vertical operation type is adopted to enable fine control of the contact surface during the fabrication process. The switch contains displacement-restricting structures in all directions for impact resistance and is packaged with anodic bonding process. The fabricated switches had an average proof mass, initial gap, and spring constant of 307.38 µg, 6.39 µm, and 3.29 N m−1, respectively. Height profile of the free-hanging proof mass was measured to show that the switch does not suffer from stress problems. In the electrostatic operation test, the contact resistance of the switch was varied with contact force and the minimum value was estimated to be 8.5 Ω. The response time of the switch was measured to be shorter than 1.2 ms. The fabricated switch operated more than 10 000 cycles without failure. For the thermal stability test, the switch was heated at 80 °C for 6 h and the switch operated successfully over 200 times. In the rotation-table experiment, the switch operated at 6.61 g and error analysis was carried out in the consideration of tangential force generated during the rotation-table experiment. From the experimental values, the tangential force was calculated as 2.375 µN and the resulting reduction in the initial switching gap was simulated as 0.32 µm. The reduced threshold acceleration thus was estimated to be 6.62 g, which agrees very well with the measured threshold acceleration value of 6.61 g.

Cost-Efficient Wafer-Level Capping for MEMS and Imaging Sensors by Adhesive Wafer Bonding.

Device encapsulation and packaging often constitutes a substantial part of the fabrication cost of micro electro-mechanical systems (MEMS) transducers and imaging sensor devices. In this paper, we propose a simple and cost-effective wafer-level capping method that utilizes a limited number of highly standardized process steps as well as low-cost materials. The proposed capping process is based on low-temperature adhesive wafer bonding, which ensures full complementary metal-oxide-semiconductor (CMOS) compatibility. All necessary fabrication steps for the wafer bonding, such as cavity formation and deposition of the adhesive, are performed on the capping substrate. The polymer adhesive is deposited by spray-coating on the capping wafer containing the cavities. Thus, no lithographic patterning of the polymer adhesive is needed, and material waste is minimized. Furthermore, this process does not require any additional fabrication steps on the device wafer, which lowers the process complexity and fabrication costs. We demonstrate the proposed capping method by packaging two different MEMS devices. The two MEMS devices include a vibration sensor and an acceleration switch, which employ two different electrical interconnection schemes. The experimental results show wafer-level capping with excellent bond quality due to the re-flow behavior of the polymer adhesive. No impediment to the functionality of the MEMS devices was observed, which indicates that the encapsulation does not introduce significant tensile nor compressive stresses. Thus, we present a highly versatile, robust, and cost-efficient capping method for components such as MEMS and imaging sensors.

齿形结构的长脉冲敏感型微加速度开关

齿形结构的长脉冲敏感型微加速度开关

Silicon MEMS acceleration switch with high reliability using hooked latch

In this study, a MEMS acceleration switch using mechanical hooked latch is designed, fabricated, and measured. A mechanical latching mechanism and switching characteristic are analyzed using FEM simulation. The acceleration switch with a size of 1.8×3.2×0.55mm3 was fabricated using a Silicon-on-Glass (SiOG) process. A resonance frequency of the fabricated switch and an acceleration threshold are measured to be 1.022kHz and 43.7g, respectively. The fabricated switch is latched when an applied external acceleration is higher than the threshold value of 43.7g. After latching “on”, the “on” state of the switch is reliably sustained regardless of the applied external acceleration.

Electrical contact performance of MEMS acceleration switch fabricated by UV-LIGA technology

This paper expanded a micro-contact resistance model to investigate the contact performance for a acceleration switch fabricated by UV-LIGA (Ultra-violet Lithographie, Galvanoformung and Abformung) technology. Based on the relationship between the contact radius a and electron mean free path ?, three different contact resistance models have been analyzed. The material properties (elastic modulus E, hardness H and Poisson's ratio v) and surface topographic parameters (asperity summit radius r, standard deviation of height distribution ?, and surface density of asperity) have been studied to evaluate the contact resistance-load characteristics. The results show that the theoretical prediction of contact resistance-load characteristics correlates well with the experimental results except there exists experimental discrepancy. The discrepancy between theoretical predictions and experimental results mainly is due to the contaminations, errors from assumptions, surface oxidation and external environmental conditions.

Simulation and characterization of dynamic contact in a MEMS passive vibration threshold sensor

A micro-machined passive vibration threshold sensor (i.e. acceleration switch) with a compliant stationary electrode has been designed, simulated and characterized. Bridge-type elastic beams as the compliant stationary electrode are adopted to improve the contact effect of the sensor. The dynamic contact between the two electrodes is simulated and analyzed by finite-element method (FEM). It is presented that a ‘skip contact’ phenomenon occurred during the switching on, which has been described and successfully explained in this paper. A drop hammer test of the fabricated vibration threshold sensor was done, which is in accordance with the simulated one. The measured two contact times in the skip contact are 16μs and 4μs under 55g applied acceleration shock, respectively, which are in agreement with simulated results.

MEMS acceleration switch with bi-directionally tunable threshold

A MEMS acceleration switch capable of tuning threshold acceleration to either higher or lower levels is designed and implemented with comb drive actuators as a mechanism of threshold tuning. A small sized switch (1.6×3.1×0.55mm3) is successfully realized by patterning silicon structures on a glass wafer. The resonant frequency of fabricated switches agrees well with a designed frequency of 1.1kHz. The threshold acceleration at no tuning voltage is 10.25g and it is subsequently tuned to 2.0g and 17.25g by applying 30V to pushing comb and pulling comb, respectively. The rising time is measured to be 9.8ms. Additional functionalities such as safe/armed position convertibility and single use latching switch are also described for diverse applications of the tunable acceleration switches.