40 results about "Quadratic nonlinearity" patented technology

The invention discloses a controllable variable-stiffness flexible elbow joint rehabilitation robot. The rehabilitation robot mainly comprises a wearable exoskeleton mechanism and non-linear driving mechanisms, wherein the wearable exoskeleton mechanism has one degree of freedom, is used for simulating the motion of an elbow joint, and mainly comprises a large arm, a small arm, a driving wheel and supporting frames; each non-linear driving mechanism comprises a motor lead screw and a connecting rod-spring non-linear mechanism; and the connecting rod-spring non-linear mechanism consists of a Robert linear mechanism and a linear spring, and the output force of the connecting rod-spring non-linear mechanism and the length change of a steel wire rope are in secondary non-linear relation. The rehabilitation robot is driven by two non-linear driving systems, and the structures of the two non-linear driving systems are similar to those of human joints. Due to the compliance of the driving systems, the safety of a patient is relatively high in the rehabilitation training process. The output force of the connecting rod-spring non-linear mechanism and the length change of the steel wire rope are in a relation of a quadratic polynomial, and the joint stiffness and the joint angle can be independently controlled, so the control accuracy of joint positions cannot be affected while the whole system keeps the flexibility.

The invention relates to the field of video image processing and provides a bit rate control method for video compression. The method comprises the following steps: A. image features are analyzed, and image feature complexity factors are calculated; B. the number of target bits which are needed to be distributed to an image is calculated; and C. quantization parameters of codes are obtained by a rate distortion model and combining the number of target bits needed to be distributed to the image. In the invention, the bit rate distribution and the image feature complexity are closely combined, and the quantization parameters Q p of codes are obtained by a secondary non-linear rate distortion model, thereby increasing the bit rate control accuracy and improving the image quality.

The application provides a method, processor, and system for performance parameter calibration of a micro-electro-mechanical-system (MEMS) acceleration sensor. A closed-loop control rotation platform is driven to carry out 360-degree-rotation multi-point positioning on a to-be-measured MEMS acceleration sensor under the field of gravity and an input shaft accelerated speed, an output shaft accelerated speed, a pendulum shaft accelerated sped, and an actual output quantity of the to-be-measured MEMS acceleration sensor are obtained; on the basis of a preset model equation, an expected output quantity is obtained; and least-square-method fitting operation is carried out the expected output value and the actual output value to obtain various model parameters of the to-be-measured MEMS acceleration sensor. The deviation value and scale factor of the to-be-measured MEMS acceleration sensor among the model parameters do not contain quadratic nonlinear coefficients, cubic nonlinear coefficients, cross coupling sensitivity and cross coupling coefficients. Moreover, an influence on the final calibration result precision by the precision limitation of the standard sensor in the prior art is eliminated and thus the calibration precision and the calibration efficiency of the system can be improved substantially.

Provided is a resonant cascaded difference frequency generator that is capable of improving the conversion efficiency of the second-order nonlinear optical phenomena by resonating the second harmonic wave of a pump light. The resonant cascaded difference frequency generator includes: a nonlinear medium, which receives a pump light and a signal light and then generates the second harmonic wave of the pump light through second harmonic generation, in a cascaded way generates a converted light of a difference frequency through difference frequency generation between the signal light and the second harmonic wave; and a resonant structure that resonates the second harmonic wave of the pump light on the basis of the nonlinear medium.

The present invention relates to a nonlinear transformation-based phase-modulated signal frequency offset estimation and tracking method. According to the method, on the basis of theoretical analysison two-phase BPSK, four-phase balanced QPSK and unbalanced four-phase UQPSK modulated signals, primary nonlinear transformation or secondary nonlinear transformation is utilized to obtain symbol influence-removed radio frequency single-carrier signals, and therefore, preconditions are created for FFT (fast Fourier transform) spectrum analysis to realize carrier frequency offset estimation fast andaccurately. Compared with existing satellite technology which directly performs processing such as FFT spectrum analysis on phase-modulated signals, the method of the invention can assist solving technical shortcomings of dispersion of envelop spectrum peak points and large frequency offset estimation error and greatly improving the accuracy and real-time performance of frequency offset estimation and tracking of the phase-modulated signals, and has a bright application prospect in realizing carrier frequency offset estimation and tracking of phase-modulated signals of different links of a satellite.

The invention relates to an aircraft overload loop design method for providing damping by adopting angular acceleration and belongs to the technical field of aircraft control. According to the method,an angular accelerometer is adopted to measure the yaw angular acceleration of an aircraft to provide damping for an overload outer loop, then an accelerometer is adopted to measure the linear acceleration of the aircraft to obtain lateral overload; the lateral overload is compared with an expected overload instruction, and therefore, an overload error signal is obtained; integration is performedon the overload error signal twice, so that an overload error comprehensive integration signal can be formed, so that a conversion static error problem between the overload instruction and an attitude instruction can be eliminated; the nonlinear transformation signal of an aircraft attitude angular acceleration signal, the proportional signal of a yaw rate and the secondary nonlinear transformation signal of an aircraft angular speed signal are introduced to form the damping signal of the overload loop, and the damping signal is output to an attitude stabilization loop, so that the control objective of overload tracking can be realized. With the method adopted, the problems of static error and insufficient damping of traditional overload control can be solved.

The invention discloses a fast encryption method for social websites. The fast encryption method for the social websites comprises the main steps of disordering for the first time, performing nonlinear encryption for the first time, disordering for the second time and performing nonlinear encryption for the second time. A password character string is disordered on the basis of the conventional message-digest algorithm 5 (MD5) encryption, so the safety of the password is enhanced; and MD5 encryption is performed for two times, so that the original text of the final ciphertext comprises character strings without logical relationship, a hacker needs a brand new original tex/ciphertext control database which does not exist at present and has huge data quantity to decode the, the difficulty of decoding the ciphertext by the hacker is greatly enhanced and the safety of the password is enhanced. The encryption flow only needs one-time communication between a client side and a server side, has low requirement on the network environment and only needs short waiting time, so the using efficiency of users is improved.

Provided is a method for estimating carrier wave or doppler frequency offset based on an approximated quadratic non-linear function in fine search, and a receiver employing the method. The method for estimating frequency offset includes the steps of: a) extracting more than three discrete samples in an order where the discrete samples are close to a maximum value of a power spectrum density function; b) inducing a quadratic non-linear function by using the extracted discrete samples; and c) estimating the frequency offset from a maximum point of the quadratic non-linear function. The technology of the present research makes it possible to exactly estimate frequency offset without increasing hardware complexity in estimation of carrier wave or doppler frequency offset.

The invention discloses a randomness testing method of pseudorandom sequence, belonging to the testing field. The method aims to solve the problem that the testing of randomness characters is limited and unilateral in the existing randomness testing method. The method comprises the following steps: firstly performing grouped linear mapping or grouped cascade linear mapping or odd integer grouped second nonlinear transformation or grouped majority voting or grouped modulo 2 additon to a sequence to be tested to obtain a new sequence after grouping process; then selecting set pair standard sequences for statistics to obtain standard statistics value DEV; counting the new sequences after grouping process to obtain new sequence statistics value dev; then calculating to obtain the biggest distance D between the standard statistics value DEV and the new sequence statistics value dev; and finally comparing the biggest distance D and the distance standard value D epsilon to judge whether the tested sequence satisfy the randomness or not. The testing method of the invention has the advantage of comprehensive testing result, reliable use and effective effect and can be widely used in fields such as measurement and range-finding, spread spectrum communication, radar navigation and data security.

A noise generation module generates power consumption noise to conceal the power consumption characteristics of a cryptographic module. The cryptographic module performs first non-linear transformation on received data, and the noise generation module performs second non-linear transformation on received data during the operational period of the first non-linear transformation.

The embodiment of the invention provides an isotropic elastic parameter amplitude-preserving inversion method and device. The method comprises the steps that the imaging inversion result of each imaging point in an isotropic elastic medium model is acquired; the imaging inversion result comprises an inverse generalized Radon transform back projection operator on a P-wave scattering field; a nonlinear inversion system is constructed based on the inverse generalized Radon transform back projection operator; an illumination matrix and a quadratic term transmission coefficient of the isotropic elastic medium model are determined; and according to the inverse generalized Radon transform back projection operator, the illumination matrix and the quadratic term transmission coefficient, the nonlinear inversion system is solved to acquire the quadratic nonlinear amplitude-preserving inversion value at each imaging point in isotropic elastic medium model. According to the embodiment of the invention, the accuracy of elastic parameter reconstruction can be improved.

A pulse compression technique for compressing femtosecond-duration high-energy pulses first linearly chirps and thus broadens an input pulse before compressing it by nonlinear soliton compression. The technique simultaneously decreases the final compressed pulse duration and improves of the compressed pulse quality. In the preferred embodiment, a linear dispersive delay (12) is employed for chirping the pulse and a single quadratic nonlinear crystal (14) is employed for nonlinear soliton compression of the pulse.

The present development includes a first element of an optical fibre entrance by which an information carrying signal is transmitted, an optical detector block, a non-linear equalizer block and a final processor block. The development includes an electrical non-linear equalizer block, connecting the output of the optical detector block and the input of the final processor block that compensates the quadratic non-linear characteristic of the optical detector block. Both blocks thus may present a more linear joint characteristic between the electrical field envelope of the information carrying signal in the optical fibre and the electrical signal. Consequently, the final processor block can compensate, in a more effective form, for the linear distortions that the information carrying signal suffers in the transmission through the fibre. The result may be an optical receiver with non-linear compensation of the photo-detection process and with approximate linear compensation of the linear distortions of the optical fibre transmission.

The invention discloses an energy demand prediction method based on a PSO-GA-SA algorithm. The method includes the following steps: selecting six energy demand impact factors including GDP, population, fixed-asset investment, energy efficiency, energy consumption structure and per capita energy consumption and taking the six factors as the input quantity of an energy demand assessment equation; adopting a secondary non-linear energy demand assessment equation; employing a PSO-GA-SA algorithm to obtain the optimal weight coefficient of the secondary non-linear energy demand assessment equation; and obtaining an energy demand prediction result in China by means of the secondary non-linear energy demand assessment equation and the six energy demand impact factors including GDP, population, fixed-asset investment, energy efficiency, energy consumption structure and per capita energy consumption. According to the method, the maximum relative error between an energy predicted value and an observed value can be controlled to be not more than 0.009%, the mean absolute percentage error (MAPE) is only 0.004%, and the prediction accuracy is high.

The invention discloses a novel vehicle positioning algorithm for an automatic parking system. The novel vehicle positioning algorithm comprises the following steps of 1, an Ackerman steering model of Ackerman offset being considered in a dead reckoning algorithm; 2, the steering transmission ratio having the nonlinear characteristic, and fitting being conducted through a quadratic nonlinear function; 3, calculating course angle increment in a dead reckoning algorithm by adopting the number of front wheel pulses; 4, calculating the unit pulse mileage in the dead reckoning algorithm by adopting a straight line and an average value calibrated under the minimum turning radius; and 5, for error correction of dead reckoning, a visual or ultrasonic sensor being adopted to identify relative parking space information, and an error of the current vehicle pose being corrected. The algorithm model is simple, the novel dead reckoning algorithm is designed based on the mileage pulse number, the vehicle body parameters and the vehicle steering angle information and considering the Ackerman offset, large computing power is not occupied, engineering application is facilitated, meanwhile, the application range is wide, and cost is low.

The invention discloses a secondary nonlinear magnetic control memristor simulator based on a current transmitter, which comprises an integral operation circuit, a multiplier M1 and a resistor R2, andthe integral operation circuit comprises a current transmitter U1, a resistor R1 and a capacitor C1. The electrical characteristics of the ports a and b of the secondary nonlinear magnetic control memristor simulator are equivalent to the port characteristics of a magnetic control memristor, the input current of the internal integral operation circuit is 0, and circuits such as a voltage followerused for avoiding the load effect do not need to be connected to the input end in series. According to the secondary nonlinear magnetic control memristor simulator, an absolute value operation circuit is not needed, only five circuit components are needed, the structure is simple, implementation is convenient, and the secondary nonlinear magnetic control memristor simulator can be widely appliedto design of various memristor circuits (circuits such as memristor chaos, memristor bridge synapses and memristor neurons).

The invention relates to a multi-phase DCDC controller design method. The method is based on a generalized multi-phase DCDC boost converter model, adopts independent control modes of all groups, comprehensively analyzes parameter uncertainty, system interference input and quadratic nonlinearity of a linear model, and establishes a robust control model of a multi-phase boost converter. The model is suitable for various circuit topologies such as single-phase boost, typical magnetic integration multi-phase boost and coupling inductance multi-phase boost, fully considers parameter uncertainty, interference input and quadratic nonlinearity, and has very high applicability and good robust stability and robust performance. A robust controller designed through the method has the advantages of being good in stability and insensitive to bounded uncertainty and interference, the system stability and transient performance requirements of a large-power multi-phase DCDC converter in a wide working range are met, and the design problem of a multi-phase staggered DCDC controller is solved.

The invention discloses a rolling bearing residual service life prediction method based on time-varying Kalman filtering, and the method can automatically match the characteristics of different degradation stages of a rolling bearing, and respectively builds time-varying Kalman filter models based on a linear function and a quadratic nonlinear function. The degeneration state of the bearing is adaptively judged according to the time-shifting window filtering relative error index factor, a Kalman filter is automatically switched to process monitoring data in different stages, and effective prediction of the remaining service life of the bearing is achieved.