Suspension system for levitation vehicles

Abstract

The performance of a passive-levitation vehicle is improved for moving over a path. The vehicle has a levitation skid slidable on the path and capable of developing a levitation force to support a compartment at a certain distance from the path. A suspension between the compartment and the skid, comprises a kinematic structure to confer degrees of freedom and relative constraints between the skid and compartment; a passive elastic element connected between the skid and the compartment; and a controlled-dynamic element able to exert a force having controlled dynamics between the skid and compartment; the passive elastic element and controlled-dynamic element mounted in parallel to each other and connected to the skid and compartment. sensor detects the distance between the skid and the path. An electronic circuit, connected to the sensor and to the controlled-dynamics element, carries out a feedback control to adjust this distance.

Claims

1. Passive-levitation vehicle for moving over a path, comprising: a passenger compartment, a levitation skid slidable on the path and capable of developing a levitation force to support the compartment at a certain distance from the path, a suspension, connected between the compartment and the skid, comprising: an articulated kinematic structure configured to confer degrees of freedom and relative constraints between the skid and the compartment; a passive elastic element connected between the skid and the compartment; a controlled-dynamic element comprising an electric actuator situated between the skid and the compartment and able to exert a force having controlled dynamics between the skid and the compartment; the passive elastic element and the controlled-dynamic element being mounted in parallel to each other and connected at their ends, respectively to the skid and the compartment; at least one sensor including a sensor for detecting the distance between the skid and the path, an electronic circuit, connected to the sensor and to the controlled-dynamics element, for carrying out a feedback control in order to adjust said distance between the skid and the path, the electronic circuit being able to read a signal emitted by the sensor, and as a function of the signal, drive the controlled-dynamic element to impose a desired course to the distance.

2. Vehicle according to claim 1, wherein the kinematic structure comprises an articulated-parallelogram connection able to allow a translational movement to the skid compared to the path causing it to remain parallel to the path.

3. Vehicle according to claim 1, wherein the suspension comprises the controlled-dynamic element to control the skid according to a roll axis and/or a pitch axis.

4. Vehicle according to claim 1, further comprising one or more passive elements configured for filtering and/or attenuating pitch and roll movements.

5. Vehicle according to claim 4, further comprising one or more passive dampers, that are configured for the filtering and/or attenuating of the pitch movements.

6. Vehicle according to claim 4, further comprising one or more passive dampers that are configured for the filtering and/or attenuating of the roll movements.

7. Vehicle according to claim 4, comprising two vertical dampers arranged at the ends of the skid that are configured for the filtering and/or attenuating of the pitch movements.

8. Vehicle according to claim 7, wherein the controlled-dynamic element is arranged between the two dampers, at an intermediate point between the two.

9. Vehicle according to claim 7, wherein elastic elements are associated to the two vertical dampers.

10. Vehicle according to claim 1, wherein the controlled-dynamic element is a variable-stiffness spring and/or a damping element with controllable damping-coefficient.

11. Vehicle according to claim 1, wherein the actuator is a linear electromagnetic actuator.

12. Vehicle according to claim 1, comprising a passive damper placed in parallel with the electric actuator.

13. Vehicle according to claim 1, wherein the electronic circuit is programmed to implement a feedback scheme to maintain constant or approximately constant the separation or gap between the skid and the path.

14. Vehicle according to claim 1, wherein an electronic circuit is programmed to implement a feedback scheme to maximize a parameter comprising a weighted sum of two or more variables that represent a constant distance of the separation between the skid and the path; and/or a vibration reduction of part or of the entire structure of the compartment; and/or a stabilization of a dynamics of the levitation skid.

15. Vehicle according to claim 1, wherein the electronic circuit is programmed to implement a real-time control based on information about the path collected previously.

16. Vehicle according to claim 15, comprising: the at least one sensor also including a sensor to detect and record data relative to the circuit, and a memory, for storing the detected data about the path, the electronic circuit being programmed to read said data from the memory and on the basis of these data perform the control of the controlled-dynamic element.

Description

(1) Further characteristics and advantages of the invention will become apparent from the description of preferred embodiments, illustrated in the accompanying drawing, in which:

(2) FIG. 1 shows a graph derived from a theoretical study;

(3) FIG. 2 shows a block diagram of a levitation vehicle;

(4) FIG. 3 shows a second diagram of a levitation vehicle;

(5) FIG. 4 shows an axonometric view of a first variant of suspension;

(6) FIG. 5 shows an isometric view of the first variant;

(7) FIG. 6 shows a side view of the first variant;

(8) FIG. 7 shows an axonometric view of a second variant of suspension;

(9) FIG. 8 shows a side view of the second variant.

(10) In the figures identical numbers indicate identical or similar parts; and to not crowd the figures some references are not repeated. The components are described as being in use.

(11) FIG. 2 shows schematically a vehicle V movable along a direction F with respect to a track S. The vehicle V comprises a passenger compartment 10, a skid 20 for levitation with respect to the track S and a suspension P between the skid 20 and the passenger compartment 10. The skid 20 allows developing a force opposing the weight of the vehicle V to support without mutual contact the passenger compartment 10 over the track S (the skid 20 is at a distance W from the track S, W being also the height of a gap between the skid 20 and the track S).

(12) In a first variant, the suspension P is composed by the parallel of a spring 22 and an active damper 24. The damper 24 is able to vary its damping constant as a function of an external signal coming from an electronic circuit 30, in turn connected to a sensor 34 capable of detecting the distance W.

(13) Preferably, the electronic circuit 30 is a microprocessor or a programmable DSP for implementing an algorithm of digital control.

(14) In general, the circuit 30 implements a feedback control with the sensor 34 for maintaining the distance W around a reference value via the driving of the controllable organs in the suspension P.

(15) The control algorithms may be different. The examples presented below are based on a non-linear quarter car model, in which a passive damper with uncontrolled damping parameter c is replaced by a controlled damper c(t).

(16) The quarter car model is given by the following equations:

(17) $\{\begin{array}{c}M\stackrel{\mathrm{.Math.}}{z}=-k\left(z-z_t\right)-c\left(\stackrel{.}{z}-{\stackrel{.}{z}}_t\right)\\ m\stackrel{\mathrm{.Math.}}{z}=-k\left(z-z_t\right)-c\left(\stackrel{.}{z}-{\stackrel{.}{z}}_t\right)+k_t\left(z_t-z_r\right)\end{array}$

(18) wherein z and z.sub.t are the coordinate of the body and of the skid; k and k.sub.t are the stiffness coefficients of the suspension and of the skid, respectively; c is the value of the damping coefficient at the instant considered; z.sub.r is a disturbance on the track S.

(19) A control strategy oriented to comfort is, for example. the States Skyhook Control (SH 2-States). This approach is based on the Skyhook phenomenon: a fictitious damper is positioned between the suspended mass and a fixed reference. When only a semi-active damper is used, vibration reduction is obtained through a control logic such as that below. The 2-States algorithm is an on/off (discontinuous) algorithm which switches between two damping values in order to meet the comfort specifications. The logic rule is:
c=c.sub.max if .Math..sub.def0
c=c.sub.min if .Math..sub.def>0

(20) Essentially, the controller deactivates the controlled damper when the speed of the body, , and the opening speed of the suspension, .sub.def=(.sub.c), have opposite signs. Such strategy has the advantage of being simple, but requires two sensors.

(21) In a second variant, see FIG. 3, the suspension P is composed of the parallel of: a spring 22, a passive damper 28 and a linear electric actuator 26 capable of applying a force between the skid 20 and the passenger compartment 10 as a function of an input signal coming from the circuit 30. The passive damper 28 is optional, and when it is present it can be controlled by the circuit 30 as the damper 24 or not.

(22) FIG. 4 shows an applicative variant of suspension 50 applied to a frame 52 of a vehicle (not shown). The suspension 50 comprises four suspension systems 54, arranged according to the corners of a rectangle, which connect the frame 52 to respective levitation skids 58. The suspension 50 is an electro-mechanical system that mechanically connects a skid 58 to the suspended frame 52. The suspension 50 carries out the suspension P of FIG. 3.

(23) A skid 58 is constituted by a surface having a series of holes (not shown) from which a certain flow of air is delivered. The lower surface of the skid 58 is planar and parallel to the surface of a rail or support S, which is also planar. To ensure safe operation of the skid 58, it is necessary to keep the two surfaces at a certain distance W. The skid 58 supports the weight of the overlying loads along the direction orthogonal to the track or support S while guarantying the motion along the tangential directions.

(24) FIGS. 5 and 6 show in detail a system 54. It comprises a connection flange 60, clampable on the frame 52, which is movably connected to a skid 58 by means of a kinematic chain 62. On the flange 60 there are mounted side by side an electromagnetic actuator 64 and a passive damper 66, which work in parallel to each other synergistically to impart a force between the frame 52 and the skid 58 via the kinematic chain 62. Such chain 62 is an articulated-parallelogram structure formed by an arm 70 and a plate 72, which are bound to each other in correspondence of four pins 74 whose axes are all parallel to each other. Two pins, the lower ones in the figure, are integral with the skid 58; the other two pins, the upper ones in the figure, are integral with the flange 60. The electromagnetic actuator 64 and the passive damper 66 have one end articulated on one side of the plate 72 via an arm 65.

(25) Overall, the kinematic chain 62 determines a translatory degree of freedom between the two surfaces of the skid 58 and of the support S. Specifically, see FIG. 6, the degree of freedom is accomplished perpendicularly to the levitation surface of the skid 58, so as to allow achieving a relative movement between the skid 58 and the frame 52 while keeping the lower surface of the skid 58 constantly parallel to that of the support S.

(26) The skid 58 is equipped with sensors, in particular

(27) a distance sensor (e.g. an inductive sensor 79 and/or a laser sensor 77); and/or

(28) an accelerometer 75.

(29) The distance sensor measures the distance W between the skid 58 and the surface of the support S. By placing more distance sensors in the skid 58 it is possible to measure the orientation of the skid 58 with respect to the support S. The accelerometer 75 measures the acceleration of the skid 58 and is present when the control system is programmed to stabilize the behavior of the skid 58 and the grip (on support S).

(30) Integrally with the flange 60 or on the frame 52, there is preferably placed (FIG. 6):

(31) an inductive sensor, and/or

(32) a laser sensor; and/or

(33) an accelerometer, indicated with 99.

(34) The inductive sensor and the laser sensor measure the distance between the frame 52 and the surface of the support or path S. These sensors are used to collect information about the profile of the path S. The accelerometer measures the acceleration or deceleration of the passenger compartment at the suspension 54. It is employed when the control system is programmed to adjust the comfort and the reduction of the vibrations transmitted to the passenger compartment.

(35) In addition to the above-mentioned sensors, a variant comprises a distance sensor to measure the stroke of the suspension 54, e.g. a rotary or linear encoder. In some cases, this sensor is integrated in the controlled-dynamic element 64. This sensor measures the stroke of the suspension 54, defined, in the case of suspension with a single degree of freedom, as the position of the suspension 54 with respect to the degree of freedom of the kinematic structure 62. In the case of suspension with multiple degrees of freedom, in order to reconstruct the position of the suspension with respect to all degrees of freedom there is a plurality of sensors equal to the number of degrees of freedom.

(36) Another variant envisages that on the vehicle's frame there is an inertial measurement device, with the function of measuring relative quantities of the vehicle's dynamics, including e.g. the attitude or height of the vehicle and the roll and pitch angles. Alternatively, such a sensor may be positioned on the skid to measure the dynamics of the same.

(37) The operation principle of the suspension 50 follows the general scheme of FIG. 3. The control unit or circuit 30 receives the signals from the sensors, from which signals it extracts the state of dynamics of the skid 58 and processes an output signal the actuators 64 are driven with.

(38) FIGS. 7 and 8 show a second variant of suspension 100 applied to a frame 102 of a vehicle 104 (shown in dashed lines). The suspension 100 carries out the suspension P of FIG. 3.

(39) The suspension 100 comprises two suspension systems 110 that connect the frame 102 to relative levitation skids 158. In this example, the skids 158 work with passive magnetic levitation, obtained e.g. through the use of a series of permanent magnets arranged according to the configuration called Hallbach-array. The magnets allow generating a levitation force in the event of relative motion with respect to a conductive surface SS which serves as track (analogous to the track S). Considering the support SS consisting of a flat surface of conductive material and arranged parallel to the plane of the skid 158 at a certain distance W, the relative motion tangential to the plane generates eddy currents in the conducting material and consequently a repulsion force perpendicular to the plane, function of the tangential speed between the two surfaces.

(40) The skid 158 comprises a wheel 156, used as a support at low speed.

(41) The two systems 110 comprise electromagnetic actuators 160, passive damping elements 162 and articulated-parallelogram kinematic structures 170.

(42) The kinematic structures 170 operate similarly to those of the first variant. Note the paralleled configuration of the electromagnetic actuator 160 and the passive element 162.

(43) The variant 100 comprises sensors analogous to those described for the variant 50.

(44) A control unit acts as in the previous variant to control the skid 158.

(45) Generally, a suspension according to the invention may allow one or more degrees of freedom between the skid and the frame. In this case there will be a controlled actuator to act respectively on each degree of freedom of the skid, preferably using proximity sensors to measure the distance and the orientation of the skid with respect to the support for sliding.