112results about How to "Good real-time control" patented technology

The present invention discloses a motor control method which uses a Space Vector Pulse Width Modulation (SVPWM). Data and instruction data are detected according to the operation state of the motor of the present carrier wave period and the modulation signal of each phase SPWM vector corresponding to the carrier wave period is computed. According to the modulation signal of each SPWM vector, the zero sequence component of the carrier wave period is added and the modulation signal of each phase SVPWM vector in the carrier wave period is obtained. The duty cycle of each phase of the carrier wave period is obtained according to the modulation signal of the SVPWM vector. Based on the duty cycle of the carrier wave period, a PWM control signal corresponding to each phase is generated. According to the PWM control signal, a PWM driving signal of the upper and lower bridge arms of a corresponding inverter is generated to control the turning on or off of each bridge arm of the inverter during the present carrier wave period. The method and device of the present invention have few steps to obtain the SVPWM signal, a simple computation and can use a cheaper chip to control the motor real time.

The invention discloses bearing-free switch reluctance motor having an axial-direction parallel hybrid structure and a control method of said motor. A motor stator is composed of a reluctance motor stator and a magnetic bearing stator. A rotor is composed of a salient pole rotor and a cylinder rotor. The windings are composed of torque windings and suspension windings. The torque windings are composed of reluctance motor windings and wide-tooth windings and the number of the torque windings is identical to phase number m. The suspension windings are two and are arranged in the radial direction. The magnetic bearing stator is composed of four E-shaped structures and the width of each middle tooth is twice of the rest. According to the invention, suspension current is calculated according to a suspension force direction. Current of the torque windings and switching-on and switching-off angles of a power circuit are controlled separately and rotation speed and torque are controlled in real time. Current of the two suspension windings is controlled separately, suspension forces are regulated in real time and mutual decoupling is realized in rotation and suspension. According to the invention, the quantity of control variables is small; suspension control is simple; and a power converter of a suspension system is low in cost.

The invention provides a multi-shaft AC servo motor control device, which comprises a parallel bus communication module, a PWM cycle counter module, an encoder feedback signal processing module, an AD interface module, a first sequential control module, a position loop computation module, a first filter group, a second filter group, a speed loop computation module, a third filter group, a data conditioning module, a CLARK transformation module, a PARK transformation module, first and second current loop computation modules, a counter electromotive force compensation module, a cross decoupling compensation module, a bus voltage compensation module, an IPARK transformation module, an ICLARK transformation module, an SVPWM module, a second sequential control module, a PWM comparator module and a dead zone insertion module. When the multi-shaft AC servo motor control device is used, the control hysteresis of a position loop, a speed loop and a current loop can be eliminated, the real-time property is good and the control precision is high; and through the global PWM cycle counter, the complete synchronization between multiple motor shafts can be realized.

The invention discloses a system for testing comprehensive performance of a metal roof. The system comprises an upper tank body (1), a lower tank body (2), a sealing piece (18), a support (21), a first air supply / exhaust device, a pump (6), a shower pipe (60), a shower nozzle (61), a refrigerator (7), a refrigerating pipe (71), an electric control device (9), a hanging rod (11), a displacement sensor (12), an electric heater (13), a net rack (14), a temperature / humidity sensor (15), and a wind pressure sensor (91), wherein a closed space is formed by the upper tank body (1) and a metal roof testing piece (8); a closed space is formed by the lower tank body (2) and the metal roof testing piece (8); the first air supply / exhaust device comprises a first fan (3) and a reversing valve (5); a reversing device is arranged in the valve body of the reversing valve (5); when the reversing device is in a first reversing state, the first fan (3) exhausts air from the upper tank body (1); and when the reversing device is in a second reversing state, the first fan (3) supplies air to the upper tank body. The system for testing the comprehensive performance of the metal roof can be widely applied to the field of test of metal roofs.

The present invention discloses a taper magnetic bearing switched reluctance motor and a control method thereof. The motor is composed of a switched reluctance motor and two taper magnetic bearings; the bias windings of the two taper magnetic bearings are connected in series with the winding of the switched reluctance motor to a form m-phase torque winding; two vertical suspension windings of each taper magnetic bearing are configured to control the suspension with two degrees of freedom, have four vertical degrees of freedom and are able to perform decoupling control; the axial suspension windings of the two taper magnetic bearings are connected in series to form an axial suspension winding for controlling the axial suspension; the motor is able to independently control the opening and closing angles of a torque winding current and power circuit to control the rotating speed and the torque in real time; and the motor is able to control five suspension winding currents to regulate the suspension forces in five directions so as to realize the suspension with five degrees of freedom. The taper magnetic bearing switched reluctance motor and the control method thereof are small in control variables, simple in suspension control and low in cost of a suspension system power converter.

The invention relates to a coreless abrasive machining measurement and control system and a corresponding coreless abrasive machining method. Combining with the fact that the coreless abrasive machining workpiece errors are mainly caused by the abrasion of a grinding wheel and a guide wheel, the coreless abrasive machining method samples and processes error signals through a workpiece error detection system in a coreless abrasive machining system, and sends the error signals to a PC computer system through a communication interface converter, and the PC computer system calculates the adjustedquantity and outputs signals to control a grinding wheel finisher, a guide wheel finisher and a feed mechanism driving system so as to achieve the finishing of the grinding wheel and the guide wheel and the adjustment of the feed mechanism. The measurement and control system and the method are mainly used for solving the problems that the prior system and the implement method thereof have a complex control method and are designed integrally.

The invention belongs to the field of additive manufacturing process detection and particularly relates to a laser three-dimensional forming process detecting system and method. A CCD molten pool detecting device, a pyrometer temperature detecting device, a structured light three-dimensional morphology detecting device, a data fusion evaluation model, a data management system and the like are mainly involved. The CCD molten pool detecting device is used for acquiring data for the molten pool state, plume and splash; the pyrometer temperature detecting device is used for acquiring molten pool center point average temperatures; the structured light three-dimensional morphology detecting device is used for acquiring data of three-dimensional morphologies of parts or the current layer or the area of and near a molten pool in the forming process; the data fusion evaluation model is used for performing fusion analysis and mutual comparative evaluation on the current data and obtaining fusioncharacteristic data; and the data management system is used for acquiring all process data including detecting data, forming process speed data, material data, motion coordinate data and the like, storing and managing the data according to a relation model, and pushing optimum process parameters according to the real-time state.

The invention provides a path tracking control method of a transfer robot based on a neural network. The method can improve the real-time performance of nonlinear model prediction control. The methodcomprises the steps: generating a training sample set through nonlinear model predictive control, wherein the training samples comprise state variables and control variables of the transfer robot; constructing a neural network model; and training the constructed neural network model by using the obtained training sample set to obtain a trained neural network model, wherein in the path tracking control process, the trained neural network model outputs a control variable, so that the transfer robot performs path tracking according to the control variable output by the neural network model. The invention relates to the field of mobile robot autonomous driving control.

The invention discloses an anomaly detection method for a vehicle-mounted CAN bus, and belongs to the technical field of information security. The invention provides an anomaly detection method of a vehicle-mounted CAN bus for message data bits of the vehicle-mounted CAN bus. According to the characteristics of the data bits, the data bits of the vehicle-mounted CAN bus message are divided into eight characteristics which respectively represent different instruction meanings and carry important control information, and the method is particularly important for anomaly detection of the data bits. Abnormality detection of CAN message data can be regarded as a dichotomy problem, normal data and abnormal data in machine learning. According to the method of the support vector machine, classification with small errors can be obtained through limited training samples, and the classification accuracy is high. According to the invention, a support vector machine (SVM) method is adopted to realize anomaly detection of the vehicle-mounted CAN bus.

The invention provides a composite structure duplex winding maglev switched reluctance motor which comprises a reluctance motor stator, a reluctance motor rotor, a conical magnetic bearing stator, a conical magnetic bearing rotor, torque windings, suspension force windings and a rotating shaft. The reluctance motor stator is of a salient pole structure, the conical magnetic bearing stator is of a conical salient pole structure, and the reluctance motor stator and the conical magnetic bearing stator are each provided with twelve teeth. The reluctance motor stator and the conical magnetic bearing stator are placed in a serial mode in the axial direction, and a gap is reserved between the reluctance motor stator and the conical magnetic bearing stator. The reluctance motor rotor is of an eight-pole structure, the conical magnetic bearing rotor is of a conical cylinder structure, and the reluctance motor rotor and the conical magnetic bearing rotor are arranged on the rotating shaft in a sleeving mode. The number of the torque windings and the number of the suspension force windings are both twelve, each torque winding is wound above the reluctance motor stator and the conical magnetic bearing stator at the same circumferential position, and each suspension force winding is wound on the conical magnetic bearing stator. The composite structure duplex winding maglev switched reluctance motor structurally achieves decoupling of the torque and the suspension force, and radial baring capacity is large; the influence of motional electromotive force on control over current chopped waves is eliminated, the real-time control effect of currents is good, high-speed adaptability is high, radial and axial suspending power is achieved, and the integration level is high.

The invention discloses an integrated circuit for driving and controlling three groups of stepper motors. The integrated circuit consists of a universal serial bus (USB) interface module, a master controller, three groups of stepper motor driving chips, three groups of two-phase stepper motors, three switching voltage regulators and a low dropout linear regulator. The master controller is a singlechip of an automatic voltage regulation (AVR) series, is connected with an upper personal computer (PC) by the USB interface module, receives data from the upper PC, processes the data, and transmitsa pulse signal and a directional signal to the stepper motor driving chips to control the accurate positioning and positive and negative rotation motions of the stepper motors. The switching voltage regulators provide working voltage for the stepper motor driving chips. The low dropout linear regulator provides reference voltage and logical voltage for the driving chips and provides working voltage for the USB interface module and the master controller. The integrated circuit for driving and controlling the stepper motors can achieve relatively higher position accuracy only by open loop control, has a simple structure and high real-time performance, and is easy to control.

The invention relates to a grain status monitoring system, belongs to the field of electrical and electronic techniques, computer techniques and automation and particularly relates to a grain status monitoring system based on a CAN (controller area network) fieldbus. The grain status monitoring system based on the CAN fieldbus comprises a management center computer (1), an RS-232 (recommended standard-232) conversion CAN fieldbus module (2), a fieldbus (3), a plurality of CAN fieldbus control terminals (4), a plurality of temperature sensors (5), a plurality of humidity sensors (6) and a plurality of contactors (7), wherein the management center computer (1) is used for completing the dynamic real-time display and accurate control of a monitoring interface, and the CAN fieldbus control terminals (4) are used for acquiring temperatures and humidities, and signals of the contactors (7), then transmitting the temperatures, humidities and signals to the management center computer (1). The grain status monitoring system provided by the invention is good in control real-time performance, vivid and accurate in monitoring interface, simple and efficient in circuit, strong in anti-jamming capability, less in cable, convenient to use and low in cost.

The invention discloses a conical magnetic suspension dual-passage switch reluctance machine and a control method. The machine comprises a switch reluctance machine and two conical magnetic bearings, wherein a bias winding of each conical magnetic bearing is connected in series with a passage winding of the switch reluctance machine to form a three-phase torque winding, two radial suspension windings of each conical magnetic bearing control suspension of two degrees of freedom, total four radial degrees of freedom exit, radial suspension forces can be in decoupling control, and a torque and axial suspension are further controlled by currents of two passage windings of the switch reluctance machine. By the switch reluctance machine and the control method, an axial suspension winding is not needed independently, suspension of five degrees of freedom can be achieved, the machine system is high in integration, a few in control variable and high in redundancy, and is simple to control.

The invention belongs to the technical field of computer systems, and discloses a signal injection-based PMSM stator winding temperature online detection method. The method comprises the steps of establishing a high-performance PMSM stator temperature online calculation method, and adding an optimal signal injection strategy into the online calculation method; adding vector control on the basis ofan existing signal injection method to form a new signal injection method; performing direct current component extraction in the new signal injection method; and calculating the stator resistance andthe estimated temperature and obtaining the real-time temperature observed data. The temperature of the stator winding of a permanent magnet synchronous motor is estimated online, so that the healthcondition of the motor can be monitored, and over-temperature generation can be prevented, and the methods can also be used in motor optimization control such as active heat management and the like, and is beneficial to improving the performance of an electric driving system.

The invention discloses a metal building element dynamic wind load simulation test device. The simulation test device comprises an upper box body(1), a lower box body(2), a seal element (3), a fan (4), a reversal valve(5), a flutter valve (6), a regulating valve (7) and a control device, wherein a reversing device (500) is arranged in the reversal valve(5), the reversal valve(5) comprises a valve air inlet, a valve air outlet, a first valve air inlet and air outlet and a second valve air inlet and air outlet, the air outlet of the fan (4) is communicated with the valve air inlet, the air outlet thereof is communicated with the valve air outlet, the second valve air inlet and air outlet are communicated with the upper box body(1), when the reversing device (500) is in a first reversing state, the valve air inlet is communicated with the first valve air inlet and air outlet and the valve air outlet is communicated with the second valve air inlet and air outlet; and when the reversing device (500) is in a second reversing state, the valve air inlet is communicated with the second valve air inlet and air outlet and the valve air outlet is communicated with the first valve air inlet and air outlet. The simulation test device of the invention can be used in the detection field of metal curtain walls and roofs.

The invention relates to idle speed control of an engine, and discloses a method for controlling idle speed of an electronically-controlled unit of a motorcycle engine. The method comprises the following steps: determining whether the engine is in an idle speed working condition or not; if so, starting the electronically-controlled unit; determining whether driving condition of an electromagnetic valve is fulfilled or not; if so, waiting for driving and calculating driving time simultaneously; transmitting a calculating result to the electromagnetic valve to drive the electromagnetic valve; checking the driving time to determine whether driving is completed or not; and if not, stopping driving the electromagnetic valve. The invention realizes excellent real-time control by the electronically-controlled unit to ensure that the engine can work at minimum rotating speed normally, and controls air input inside a cylinder based on the best air-fuel ratio to ensure that fuel of the engine can be combusted more sufficiently under the idle speed working condition, thereby reducing content of harmful gases in tail gas emission at this moment, and achieving specified emission standard.

The invention discloses an internet-of-things gateway achieving IP virtualization conversion. The internet-of-things gateway comprises two real network adapters which are simultaneously connected with a network adapter scheduling module, one real network adapter is a main real network adapter, and the other real network adapter is a standby real network adapter; the network adapter scheduling module is connected with a data storage module and at least two virtual network adapters, each virtual network adapter is correspondingly connected with a data communication module, at least one data communication module is connected with a signal input module, and the other data communication module is connected with a signal output module; the signal input module is connected with a sensor, and the signal output module is connected with an agriculture control device; an input channel is formed between the signal input module and the corresponding virtual network adapter, and an output channel is formed between the signal output module and the corresponding virtual network adapter.

The invention relates to a motor controller of a layering multinuclear structure and a control method thereof. The motor controller comprises a power contravariant unit driving a motor to operate, an application interface function module, a motor control function module and a driving function protection module, the application interface function module sends state information of the controller to an external control system, receives control signals and sends control commands to the motor control function module; the motor control function module receives the control commands, detects states of the motor, completes control operation and sends control pulses to the driving function protection module; the driving function protection module receives the control pulses, processes the control pulses and sends the control pulses to the power contravariant unit; and the driving function protection module detects operating states of an inverter and controls the power contravariant unit. The motor controller is divided into three layers of independent systems from inside to outside and from bottom to top, the three layers of independent systems increase a driving layer system, a control layer system and an application layer system, all modules are tightly connected, functions are relatively independent, system breakdown is avoided under extreme cases, reliability is high, and safety is strong.

The invention discloses a micro-controller used for motor control. The micro-controller used for motor control is characterized by comprising a processor, a storage unit, a clock generation unit, a math co-processor, a programmable analog amplifier, an analog-to-digital converter, a motor control unit, a comparator and a bus unit. The processor, the storage unit, the clock generation unit, the math co-processor, the programmable analog amplifier, the analog-to-digital converter, the motor control unit and the comparator are connected via the bus unit.

The invention relates to a management system for relations of hospital clients, which comprises a service processing module connecting with the data base of the server, a calling device and an agent interface. The hospital client-side is connected with the calling device via the agent interface, according to the received information of the calling device, the server records the client data, client condition, calls the data base and makes resource allocation treatment, according to the need of the client, the server finds out the adapting data and generates report or reservation result. The management system for relations of hospital clients of the invention is an intelligent management system with high efficiency, large volume and multiple function which links hospital and the client. Additionally, the invention has functions of data collecting, data statistical analyzing, real-time reservation and the like and is capable of providing data analyzing reports of three big categories of operation, behavioral analysis and scientific research prediction.

The invention provides a safeguard system of a rubber wheel car. When the vehicle exceeds limit first-level vehicle speed, an exhaust brake closes a butterfly valve and stops supplying fuel oil, in this way, kinetic energy of the vehicle is consumed, and an auxiliary braking effect is achieved; when the vehicle does not achieve an expected speed reduction effect under the auxiliary effect of the exhaust brake, and the vehicle speed exceeds limit second-level set vehicle speed, an air-cut brake of the vehicle is automatically started and plays a role in brake speed reduction; under the condition that stalling happens on the car, current two levels of brake systems can not effectively achieve the brake effect, and the vehicle speed exceeds limit third-level vehicle speed, a control system will automatically start a roadway road surface intercepting mechanism to effectively intercept the vehicle with stalling. The system is simple in structure, high in practicability and easy to refit on a common mine vehicle, intelligently controls the vehicle speed and intercepts the vehicle with stalling.

The present invention relates to a sweeping robot video monitoring method and a server. The sweeping robot video monitoring method comprises the steps of using the server to receive a video communication request coming from a terminal via a public platform; according to the video communication request, generating a corresponding video communication instruction; sending the video communication instruction to a sweeping robot; providing the video data to the terminal via the public platform, wherein the server records a correlation relation of the terminal and the sweeping robot. According to the sweeping robot video monitoring method and the server of the present invention, the correlation relation between the sweeping robot and the terminal can be established on the condition of not increasing the structure complexity and the cost of the sweeping robot excessively, thereby providing the video data coming from the sweeping robot to the terminal.

The invention discloses a conical magnetic suspension switch reluctance motor and a control method. The motor consists of a switch reluctance motor and two conical magnetic bearings; bias windings of the two conical magnetic bearings are connected with a winding of the switch reluctance motor in series to form a three-phase torque winding; two radial suspension windings of each conical magnetic bearing control suspension of two degrees of freedom, so that four radial degrees of freedom is formed and decoupling control can be realized; the axial suspension windings of the two conical magnetic bearings are connected together in series to form one axial suspension winding to control axial suspension; the motor can independently control torque winding current and turn-on and turn-off angles of the power circuit, and can control rotary speed and torque in real time; current of five suspension windings is controlled, suspension force in five directions can be adjusted in real time, and suspension of five degrees of freedom can be further realized; and the motor and the control method disclosed by the invention are high in integration degree, less in control variables and simple in suspension control, and the power converter of the suspension system is low in cost.

The invention provides an ankle joint rehabilitation mechanism based on RRR-PaRPS-RHJ. The ankle joint rehabilitation mechanism comprises a base, a first support rod, a second support rod, a foot pallet and a rotary unit. The first support rod and the second support rod are both fixed on the base. A first motor is arranged on the base. One end of the foot pallet is rotatably connected with a second motor arranged on the first support rod through a first connecting rod. The other end of the foot pallet is rotatably connected with the rotary unit through a second connecting rod in order to achieve universal rotation of the foot pallet. The rotary unit comprises a first branched chain and a second branched chain rotatably connected with the first branched chain. One end of the first branchedchain is rotatably connected with a third motor arranged on the second support rod. The other end of the second branched chain is rotatably connected with the first motor. The first branched chain andthe second branched chain drive the foot pallet to stimulate inwardly-turning, outwardly-turning, plantar flexion, backwardly bending, inwardly rotary and outwardly rotary moves of an ankle joint ofa human body.

A DC voltage balance control strategy for cascade multi-level pow electronic converter with single-direction energy flow is compose of sequencing module, matching module, operation module and modulation wave generation module. The invention improves the traditional one-cycle control, in addition to the advantages of not changing the use of a phase locked loop for one cycle control and the use of avoltage sensor for the ac side, Compared with the DC voltage balance control strategy based on traditional PI control, the adjustable speed is fast, Advantages of wide adjustment range, when the unbalance of DC voltage of cascaded multi-level power electronic converters with one-way energy flow is large, the unbalance of DC voltage of cascaded multi-level power electronic converters with one-wayenergy flow is large, The method of the invention can make the cascade multi-level power electronic converter with energy flow in one direction to regulate the DC voltage of each stage at the maximumrate to keep the balance, and make the AC side of the whole circuit run under the condition of low harmonic and high power factor.

The invention discloses a water distiller monitoring system based on a Profibus. The water distiller monitoring system comprises a monitoring center upper computer installed with industrial control configuration software, a Profibus / RS232 conversion module, the Profibus, a plurality of Profibus control terminals for carrying out field data acquisition and control on a water distiller and a signal acquisition device and an execution mechanism device which are connected with the Profibus control terminals respectively, the Profibus control terminals comprise controllers, signal conditioning circuits, data acquisition circuits, data merge processors, photoelectric couplers, Profibus transceivers and electromagnetic valve driving circuits. The water distiller monitoring system is simple in structure, reasonable in design and high in automation degree and works to carry out comprehensive and real-time monitoring on a distilled water production process to fundamentally guarantee the distilled water production quality and reduce the operation cost.

The invention provides an energy management method of an intelligent microgrid. The method comprises the following steps of acquiring Internet power Pdgrid, Internet power threshold value Pdth and output power Pp of a photovoltaic cell of the intelligent microgrid in real time; if Pp is equal to 0, removing all photovoltaic cells in the intelligent micorgrid, and revising output power PE of an energy storing device; and if Pp is larger than 0, removing and inputting the photovoltaic cells according to a working condition of the energy storing device. Compared with the prior art, according to the energy management method of the intelligent microgrid, power of a call wire is compensated through the energy storing device, the problem of reverse-power is avoided, and effective monitoring on the intelligent microgrid can be realized under the conditions of environment mutation, and immediate reaction not allowed at hardware environment.

The invention discloses a hybrid electromagnetic magnetic bearing switch reluctance motor. The hybrid electromagnetic magnetic bearing switch reluctance motor is composed of a motor stator, a reluctance motor rotor, a magnetic bearing stator, 12 torque windings, 12 suspension force windings and a rotating shaft; each of the reluctance motor stator and the magnetic bearing stator comprises 12 poles, the reluctance motor stator and the magnetic bearing stator are arranged in series in the axial direction, and a gap is formed there-between; the reluctance motor rotor comprises 8 poles, the magnetic bearing rotor is cylindrical, both the reluctance motor rotor and the magnetic bearing rotor sleeve the rotating shaft, and a gap which is equal to the distance between the magnetic bearing stator and the reluctance motor rotor is formed between the reluctance motor rotor and the magnetic bearing rotor; each torque winding winds a reluctance motor stator tooth and a magnetic bearing stator tooth in the same circumferential position, and each suspension force winding winds a magnetic bearing stator tooth. By means of the structure, the hybrid electromagnetic magnetic bearing switch reluctance motor realizes to decouple the torque and suspension force, and the radial bearing force is large; the influence of motion electromotive force on the suspension current chopping control is avoided, the real-time control effect of the current is good, and the high-speed adaptability is strong.

The invention discloses a collaborative robot constant-force massage method based on a PID algorithm. The method comprises following steps: equipment is mounted; a power-on button on a robot demonstrator is pressed, and a robot control system is powered on; a human-computer interaction software program is operated on an upper computer, a human-computer interface is started, and a constant-force value and a stepping value of constant-force massage are set by a user; a communication channel with the upper computer is constructed; a displacement compensation value and a posture compensation valueare calculated according to a force value and a torque value, measured by sensors, of a robot terminal; robot terminal force is corrected by the calculated compensation values; the massage is completed, the upper computer stops operation, and the robot stops movement. The massage effect is good, and the human comfort is higher; the method is simple to operate, good in real-time property, low in noise and higher in safety; the posture of the robot can be adjusted automatically in the massage process, and the level of intelligence is higher; the robot is less affected by external disturbance, and the robustness is good.

The invention discloses a data collection and transmission system based on a vibration wire sensor. The data collection and transmission system is characterized by comprising a control unit and a communication unit. The control unit comprises a power module, a control module, a GPRS (General Packet Radio Service) module, a collection module and a sensor module. A work method comprises the steps of power on, power supply mode switch, signal collection, diagnosis and display, data analysis and display, parameter setting instruction sending. The data collection and transmission system has the advantages of being simple in device, achieving modularization processing, being easy to communicate, collecting data regularly and in real time, being low in power consumption, being good in stability and improving data collection efficiency. The GPRS module and the collection module can be selectively powered on, are powered on when working and are powered down when not working, so that the whole data collection and transmission system are in a low power consumption mode.