Piezoelectric steering engine of bistable and control method thereof

Abstract

A piezoelectric steering engine of bistable includes a base, four torsion units respectively fixed on the base, and four stiffness devices respectively located at a free end of the four torsion units. The four torsion units share the same structure, and are sequentially arranged at an interval of 90° in a same plane. The four stiffness devices share the same structure and are all connected to rudder blades. Every torsion unit includes a cantilever beam, a first macro-fiber composite actuator and a second macro-fiber composite actuator both of which are respectively attached to two opposite surfaces of the cantilever beam. A first stiffness device includes an elastic ring and a bearing pad mounted inside the elastic ring. After the cantilever beam passes through the bearing pad, a torque is exerted on the cantilever beam by the elastic ring through the bearing pad, resulting in the buckling of the cantilever beam.

Claims

1. A piezoelectric steering engine, which comprises: a base (10), a first torsion unit (1) fixed on the base (10), a first stiffness device (2) located at a free end of the first torsion unit (1), a second torsion unit (3), a second stiffness device (4) located at a free end of the second torsion unit (3), a third torsion unit (5), a third stiffness device (6) located at a free end of the third torsion unit (5), a fourth torsion unit (7), a fourth stiffness device (8) located at a free end of the fourth torsion unit (7), wherein: all of the first torsion unit (1), the second torsion unit (3), the third torsion unit (5) and the fourth torsion unit (7) are same in structure and are sequentially arranged at an interval of 90° in a same plane; all of the first stiffness device (2), the second stiffness device (4), the third stiffness device (6) and the fourth stiffness device (8) are same in structure and are connected with rudder blades; the first torsion unit (1) comprises a cantilever beam (1-1), a first macro-fiber composite actuator (1-2) and a second macro-fiber composite actuator (1-3) both of which are respectively attached to two opposite surfaces of the cantilever beam (1-1); the first stiffness device (2) comprises an elastic ring (2-1) and a bearing pad (2-2) mounted inside the elastic ring (2-1); the cantilever beam (1-1) passes through the bearing pad (2-2), an inner diameter of the bearing pad (2-2) is smaller than a width of the cantilever beam (1-1), so that after the cantilever beam (1-1) is mounted inside the first stiffness device (2), a torque is exerted on one end of the cantilever beam (1-1) by the elastic ring (2-1) through the bearing pad (2-2), resulting in buckling of the cantilever beam (1-1).

2. The piezoelectric steering engine according to claim 1, wherein: all of the first torsion unit, the second torsion unit, the third torsion unit, the fourth torsion unit, the first stiffness device, the second stiffness device, the third stiffness device and the fourth stiffness device are mounted inside an outer cover (9) and pass through the outer cover (9) to be connected with the rudder blades.

3. A control method of the piezoelectric steering engine according to claim 1, the method comprising: while the piezoelectric steering engine is not energized, enabling the cantilever beam (1-1) to be in a first unstable deflection state by the elastic ring (2-1) applying a pre-stress to the cantilever beam (1-1), wherein the cantilever beam (1-1) is deflected by an angle which is defined as α; in an initial state, simultaneously applying a half full-scale voltage to the first macro-fiber composite actuator (1-2) and the second macro-fiber composite actuator (1-3) which is opposite to the first macro-fiber composite actuator (1-2), offsetting a torque of the first macro-fiber composite actuator (1-2) with a torque of the second macro-fiber composite actuator (1-3), remaining the cantilever beam (1-1) in the first unstable deflection state; while the piezoelectric steering engine needs to be controlled, twisting and deforming the cantilever beam (1-1) by applying a rising voltage to the first macro-fiber composite actuator (1-2), increasing the rising voltage to a maximum control voltage, simultaneously applying a falling voltage to the second macro-fiber composite actuator (1-3), and decreasing the falling voltage to a minimum control voltage, and then changing the cantilever beam (1-1) from the first unstable deflection state to a second unstable deflection state, wherein the cantilever beam (1-1) is deflected by an angle which is defined as −α; when the cantilever beam (1-1) is deflected by the angle of −α, twisting and deforming the cantilever beam (1-1) by applying the falling voltage to the first macro-fiber composite actuator (1-2), decreasing the falling voltage to the minimum control voltage, simultaneously applying the rising voltage to the second macro-fiber composite actuator (1-3), increasing the rising voltage to the maximum control voltage, and then changing the cantilever beam (1-1) from the second unstable deflection state to the first unstable deflection state, wherein the cantilever beam (1-1) is deflected by the angle of α.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a stereogram of a piezoelectric steering engine of bistable provided by the present invention.

(2) FIG. 2a is an assembled diagram of a first torsion unit and a first stiffness device.

(3) FIG. 2b is a structurally schematic view of the first stiffness device.

(4) FIG. 2c is a structurally schematic view of the first torsion unit.

(5) FIG. 3a is a schematic view of the first torsion unit in a first unstable deflection state.

(6) FIG. 3b is a top view of the first torsion unit in the first unstable deflection state.

(7) FIG. 4a is a schematic view of the first torsion unit in a second unstable deflection state.

(8) FIG. 4b is a top view of the first torsion unit in the second unstable deflection state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(9) The present invention is further described in detail with accompanying drawings and embodiments as follows.

(10) As shown in FIG. 1, a piezoelectric steering engine of bistable provided by the present invention comprises a base 10, a first torsion unit 1 fixed on the base 10, a first stiffness device 2 located at a free end of the first torsion unit 1, a second torsion unit 3, a second stiffness device 4 located at a free end of the second torsion unit 3, a third torsion unit 5, a third stiffness device 6 located at a free end of the third torsion unit 5, a fourth torsion unit 7, a fourth stiffness device 8 located at a free end of the fourth torsion unit 7, wherein: all of the first torsion unit 1, the second torsion unit 3, the third torsion unit 5 and the fourth torsion unit 7 share a same structure, are sequentially arranged at an interval of 90° in a same plane; all of the first stiffness device 2, the second stiffness device 4, the third stiffness device 6 and the fourth stiffness device 8 share a same structure and are connected with rudder blades.

(11) As shown in FIGS. 2a, 2b and 2c, the first torsion unit 1 comprises a cantilever beam 1-1, a first MFC (macro-fiber composite) actuator 1-2 and a second macro-fiber composite actuator 1-3 both of which are respectively attached to two opposite surfaces of the cantilever beam 1-1; the first stiffness device 2 comprises an elastic ring 2-1 and a bearing pad 2-2 mounted inside the elastic ring 2-1; the cantilever beam 1-1 passes through the bearing pad 2-2, an inner diameter of the bearing pad 2-2 is smaller than a width of the cantilever beam 1-1, so that after the cantilever beam 1-1 is mounted inside the first stiffness device 2, a torque is exerted on one end of the cantilever beam 1-1 by the elastic ring 2-1 through the bearing pad 2-2, resulting in the buckling of the cantilever beam 1-1. After the buckling, the cantilever beam has two stable states, namely, a deflection angle of the cantilever beam after being twisted is α or −α.

(12) An actuating method of the present invention is described in detail as follows.

(13) While being not energized, as shown in FIGS. 3a and 3b, due to the pre-stress of the elastic ring 2-1, the cantilever beam 1-1 is in a first unstable deflection state and has a deflection angle of α; in an initial state, a half full-scale voltage is simultaneously applied to the first macro-fiber composite actuator 1-2 and the second macro-fiber composite actuator 1-3, and at this time the two actuators are opposite to each other, two corresponding torques are offset from each other, the cantilever beam 1-1 remains in the first unstable deflection state. When it is required to control the steering engine, a rising voltage is applied to the first macro-fiber composite actuator 1-2, the rising voltage is increased to a maximum control voltage, and simultaneously a falling voltage is applied to the second macro-fiber composite actuator 1-3, the falling voltage is decreased to a minimum control voltage, so that the cantilever beam 1-1 is twisted and deformed, simultaneously changes from the first unstable deflection state to a second unstable deflection state, and has the deflection angle of −α, as shown in FIGS. 4a and 4b. When the deflection angle is −α, if a falling voltage is applied to first macro-fiber composite actuator 1-2, the falling voltage is decreased to the minimum control voltage, and simultaneously a rising voltage is applied to the second macro-fiber composite actuator 1-3, the rising voltage is increased to the maximum control voltage, so that the cantilever beam 1-1 is twisted and deformed, changes from the second unstable deflection state to the first unstable deflection state, and has the deflection angle of α.

(14) Through the method as same as the above description, all of the second torsion unit 3, the third torsion unit 5 and the fourth torsion unit 7 are able to control the rudder blades.