52 results about "Unstable equilibrium" patented technology

A collapsible sun shade, including: a shade; at least two supports, each support having a first end and a second end, with the second end of each support coupled to the shade at spaced-apart locations thereof; and a connector coupled to the first end of each support; wherein the shade is adapted to assume an unstable equilibrium position in which the supports and the shade are substantially coplanar with the connector, a collapsed position when the shade and supports are on one side of the unstable equilibrium position in which the shade is folded, and a deployed position when the shade and supports are on the other side of the unstable equilibrium position in which the supports and the shade are expanded.

A pop-pin and a method for using the pop-pin with a weight-training machine to perform mixed-weight sets of exercise are disclosed. A pop-pin having a spring loaded into an unstable equilibrium position can be inserted into a weight stack to select a weight and vertical guide bar while another conventional pin is inserted into the same weight stack and the vertical guide bar at a position above the pop-pin. A user can then operate the weight-training machine, at which point the spring on the pop-pin is dislodged from the unstable equilibrium position and presses on the weight plate into which it is inserted. When the weight stack is lowered, thus reducing the load of weight on the pop-pin, the force of the spring pressing against the weight plate ejects the pop-pin from the weight plate. At this point, the user can continue the exercise with the smaller stack.

The invention relates to an electromechanical actuator 100 for hearing applications comprising one or more permanent magnets 10 and one or more magnetically permeable members 20 arranged to form a stator 50 and armature 70 arranged to provide one or more magnetic flux circuits 80, 80′ configured to give rise, in the armature seat 52, to a position of unstable equilibrium for the armature 70 along the longitudinal A-A′ axis and regions either side of the position of unstable equilibrium along the longitudinal A-A′ axis where the armature applies a destabilization-driven force to the compliant member that decreases the effective rigidity of the compliant member that retains to armature in a neutral position. The invention also relates to a hearing aid system incorporating the electromagnetic actuator.

A detachable grip device has a body, two jaw-forming elements which are mobile in relation to each other between an open position and a closed position, a system for displacing the jaw-forming elements which are designed in such a way as to be able to alternate between a stable closing state and a stable opening state, via an intermediate state of unstable equilibrium, and a system for opening the jaw-forming elements. The opening system is adapted in such a way as to drive the displacement system initially in their closed state past the intermediate state of unstable equilibrium. The opening system comprises at least one button which is arranged on a longitudinal side of the body and is mounted in a sliding manner according to a direction of displacement having a component in the transverse direction.

The invention relates to a power system transient stability discrimination method based on a phase trajectory and a relative kinetic energy change rate. The power system transient stability discrimination method comprises the steps of: acquiring information of a generator set in a power system at one moment; then judging whether the power system fails or not, and if so, equating the whole set witha single generator; calculating a phase trajectory concavity and convexity index of the equivalent single generator, and judging the stability of the system according to the index; calculating the relative kinetic energy change rate of the system, performing derivation on the relative kinetic energy change rate, regarding a first derivative as an auxiliary criterion for transient instability, andjudging whether the system is in transient instability according to the auxiliary criterion; and if the auxiliary criterion for transient instability is not met, judging transient stability of the system through judging whether the system reaches an unstable equilibrium point, acquiring generator set information at a next moment if the system does not reach the unstable equilibrium point, and cycling the above steps to judge the transient stability of the system. The power system transient stability discrimination method comprehensively applies the phase trajectory concave and convexity and the relative kinetic energy change rate criteria, and can judge the transient stability of a multi-generator system accurately, quickly and timely.

Disclosed is a vehicle cab turnover device, in particular to a vehicle cab hydraulic turnover which enables the vehicle cab drop automatically to the lowest point after climbing over the unstable equilibrium point of barycenter. The invention solves the technical problem that the damping device which produces a damping effect during the process of the vehicle cab barycenter climbing over the unstable equilibrium point and turning over forward to the lowest point does not play damping effect when the vehicle cab climbs up forward from the initial position to the unstable equilibrium point of barycenter and when the vehicle cab turns over backward from the lowest point to the initial position. The invention is characterized in that an active damping plug is arranged between a spherical one way valve and a reset spring of a reversing valve with an output one-way valve in the oil pump main body. The invention can not only avoid the vehicle cab fast falling to the lowest point after climbing over the unstable barycenter equilibrium point, but also save additional stroke control device; and has a small operation torque and high mechanical efficiency.

The present invention discloses a power grid transient stability energy function analysis method and system containing a detailed generator model. The method comprises the following steps of: establishing a power system model containing the detailed generator model; determining a failure mode; calculating an angular point CRN; calculating a generator equivalent parameter; solving an accurate controlling unstable equilibrium point (CUEP); and calculating an energy margin according to a system energy difference value of the CUEP and a failure clearing moment. The system comprises apparatuses used for implementing the method. The problem of a relatively large deviation between a transient stability analysis result and an actual situation, caused by a too simplified model in an existing energy function method entering a practical stage, is solved, so that the reliability of power system security analysis can be improved.

The invention discloses a critical cluster identifying method for transient stability analysis of a power system. The critical cluster identifying method comprises the following steps: obtaining a critical clearing time of a fault by using time domain simulation; obtaining a critical stable track and a critical unstable track of the power system according to the critical clearing time; determining a leading unstable balance point according to the critical stable track and the critical unstable track so as to obtain a power angle of each generator at the leading unstable balance point; carrying out simulation according to the actual clearing time of the fault so as to obtain a fault track; calculating the sensitivity of an energy margin to the mechanical power of each generator according to the fault track and the power angle of each generator at the leading unstable balance point; and identifying generators of a predetermined number in the generators, of which the calculation results of the sensitivities are negative values, as the critical cluster. According to the critical cluster identifying method for transient stability analysis of the power system, the critical cluster is identified according to the sensitivity of the mechanical power of each generator based on the energy margin; the identification accuracy is improved; and the situation of misjudgment is reduced.

The invention relates to a method for sorting transient severe faults of a power system. The method includes a first step of trend data and stable calculating data; a second step of generating a power grid model, a third step of analyzing ground state trend, a fourth step of initially forming predefined faults, a fifth step of determining and sorting at a post-fault balance point, a sixth step of determining and sorting inertia transient, a seventh step of determining and sorting post-inertia transient, an eighth step of determining and sorting an exit point, a ninth step of determining and sorting inertia transient of a minimal gradient point, a tenth step of determining and sorting post-inertia transient of the minimal gradient point, an eleventh step of determining and sorting the minimal gradient point, a twelfth step of determining and sorting faults under an unstable equilibrium point, and a thirteenth step of obtaining a related severe fault list. Content determination standards of different important nodes during a fault trajectory process are fully considered from aspects of the post-fault balance point, the exit point, the minimal gradient point and the related unstable equilibrium point through calculation, and reliability and accuracy of fault scanning are ensured.

The invention discloses a resonant sonic toothbrush for preventing the phenomenon that the main shaft of a resonant sonic toothbrush may not rotate. A permanent magnet assembly comprises a magnetic core and a magnet, wherein the magnetic core is fixed on the main shaft; at least two slots are formed in the circular array on the outer wall of the magnetic core; and two magnets are arranged in each slot, the N pole of one magnet is arranged outward along the radial direction of the main shaft, and the S pole of the other magnet is arranged outward along the radial direction of the main shaft. According to the toothbrush, two magnets with opposite magnetic poles are arranged in one slot in the magnetic core, the magnetic field generated by a stator winding is attractive to one magnet and is repellent to the other magnet, a torque is naturally formed to drive the main shaft to rotate, unstable balance point cannot occur, and the reciprocating rotation of the main shaft can be relatively stable.

The invention discloses a method for solving a transient voltage stability safety region of an AC/DC system, which utilizes an energy function method and a singular induced bifurcation theory to analyze the transient voltage stability of the AC/DC system respectively. Based on the characteristics of transient potential energy of dynamic components in AC/DC system, the parameter space of key dynamic components used to describe the safety region is found. Furthermore, the boundary of the transient voltage stability security region determined by the stability manifold and singular surface of thetransient voltage instability-dependent dominant unstable equilibrium point is constructed. Then the boundary of the safety region determined by the stable manifold of the transient voltage instability-dependent dominant unstable equilibrium point and the boundary of the safety region determined by the singular surface are obtained by Q-linear approximation and second-order Taylor expansion respectively. By analyzing the influence of a plurality of dynamic components on the transient voltage stability in a multi-machine system, the invention selects key parameters to form a dynamic safety region space, which is favorable for an operator to quickly and effectively monitor the system.

Systems and methods to that facilitate stability of an FRC plasma in both radial and axial directions and axial position control of an FRC plasma along the symmetry axis of an FRC plasma chamber. The systems and methods exploit an axially unstable equilibria of the FRC to enforce radial stability, while stabilizing or controlling the axial instability. The systems and methods provide feedback control of the FRC plasma axial position independent of the stability properties of the plasma equilibrium by acting on the voltages applied to a set of external coils concentric with the plasma and using a non-linear control technique.

The invention provides a method for formulating a transient stability emergency control generator tripping scheme for an interconnected network. The method comprises the steps of carrying out time-domain simulation on a network fault for which a generator tripping scheme needs to be formulated, extracting phase trajectory information of critical unit pairs and judging whether power angle instability of a system appears or not when an accident occurs; if the power angle instability does not appear, not carrying out generator tripping; and if the power angle instability appears, identifying critical units according to angular velocity information, carrying out stand-alone equivalent calculation on a critical cluster, calculating a generator tripping value, sorting the critical units according to the rotating speed at the generator tripping moment and selecting a generator tripping object according to the sorting result. According to the setting method, an instability fault can be judgedonly through extracting the phase trajectory information of the critical unit pairs, and the generator tripping value can be obtained only through carrying out stand-alone equivalent calculation on the critical cluster and collecting the angle of a power-angle curve of a stand-alone equivalent system of the critical cluster at the generator tripping moment, the angle and angular velocity at the moment of passing through an unstable equilibrium point, and the angle and power information of 10 sampling moments after passing through the unstable equilibrium point, so that the method provided by the invention is simple in scheme formulating process and high in efficiency in comparison with a traditional method.

The invention relates to a device for controlling the shifting of a propeller turbine engine into reverse mode, by acting on a shaft (13) for controlling the pitch of the propellers. The device comprises: at least one centrifugal weight (14) arranged to drive the propellers into the flag position thereof under the action of the centrifugal force; and an actuator (9) that can rotate the control shaft (13) in order to shift the pitch of the propellers from a traction mode to a reverse mode, passing through a zero pitch position. The invention is characterised in that the centrifugal weight (14) is in an unstable equilibrium position in relation to the action of the centrifugal force when the control shaft shifts the pitch of the propellers (6) through the zero pitch position. In addition, the invention comprises an actuation means (19) that exerts a torque on the control shaft (13) when the centrifugal weight is in the unstable equilibrium position, so as to prevent it from staying in this position.

The invention is directed at an optical sensor device, comprising a sensing element for receiving an input action, an optical fiber comprising an intrinsic fiber optic sensor, and a transmission structure arranged for exerting a sensing action on the optical fiber in response to the input action received by the sensing element, wherein the optical fiber in a first connecting part thereof is connected to a reference body and wherein the optical fiber in a second connecting part thereof is to the transmission structure for receiving the sensing action, the first connecting part and the second connecting part of the optical fiber being located on either side of the intrinsic fiber optic sensor, wherein the transmission structure comprises a bi-stable spring having a first and a second stable deflection position and a negative stiffness range around an unstable equilibrium position between the first and second stable deflection position, and wherein the optical fiber between the transmission structure and the reference body is pre-stressed such as to be tensed, said optical fiber thereby acting as a spring having a first spring constant of positive value, wherein the optical fiber thereby counteracts a spring action of the bi-stable spring such as to operate the bi-stable spring in a deflection position range within the negative stiffness range, the deflection position range not including the unstable equilibrium position of the bi-stable spring.