JPH03213500A - Gravity-free simulating device - Google Patents

Abstract

PURPOSE:To facilitate production of the gravity-free state of an object by mounting a test piece on an active drive mechanism, having at least six degrees of freedom, through a sensor, and effecting feedback of the active drive mechanism so that a detecting force and torque are balanced with gravity of the test piece. CONSTITUTION:An active drive mechanism 2, e.g. an industrial robot, is located on a ground 1, and a test piece 4 is mounted on the active drive mechanism 2 through a sensor 3 to detect a force and torque. The sensor 3 is arranged so as to allow detection of the forces of X-Z-axes and torque around the X-Z- axes. The active drive mechanism 2 is formed so that an object 4 can be actively driven in orientation to roll, pitch, and yaw around each of X-Z-axes. Feedback control is made on the active drive mechanism 2 so that a force and torque detected by the sensor 3 are balanced with gravity of the test piece 4, and feed forward control is effected according to the speed detecting value of the test piece.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a weightless simulator for simulating the motion of an object after a collision in a weightless state, such as docking of a spacecraft. Regarding.

Conventional technology Some of the movements associated with various mission operations in space include:
There are many actions that can be mechanically regarded as contact and collision phenomena of floating objects, including capture and combination actions. In order to design and manufacture equipment and formulate work plans so that work involving contact and collision can be carried out smoothly without any problems, we must
It is necessary to know as accurately as possible how the object of interest behaves when it comes into contact or collision. The most direct and effective method for this purpose is to recreate the floating state of an object in space on the ground.

Conventionally, the following methods have been used for reproduction experiments on the ground, but each method has the following problems. Air levitation and magnetic levitation type experimental devices have the disadvantage that the motion of objects is limited to in-plane motion and cannot simulate three-dimensional spatial motion.

Additionally, underwater experiments in which gravity and buoyancy are balanced have had the problem that the dynamic characteristics of objects change due to water resistance and added mass.

Furthermore, simply attaching an object to a 6-degree-of-freedom motion mechanism (for example, a device composed of a girder and gimbal mechanism) will affect the motion of the object itself because the mass characteristics of the motion mechanism will affect the motion of the object. There was a problem that it could not be reproduced.

In addition, the computer has an equation of motion model for the object,
The method of moving an object by numerically calculating its motion moment by moment is
The problem was that it was a heavy burden on the computer, making it unsuitable for real-time simulation.

Furthermore, creating a zero-gravity environment on a drop platform or inside an aircraft requires large-scale equipment and is not suitable for simulating long-term motion.

Problems to be Solved by the Invention An object of the present invention is to provide a zero-gravity simulating device that can easily realize a three-dimensional zero-gravity state in real time.

Means for Solving the Problems The present invention provides an active drive mechanism that divides a test object into at least six degrees of freedom, and a force and torque interposed between the active drive mechanism of the test object and acting on the test object. and a means for controlling the active drive mechanism in response to the output of the sensor so that the force and torque detected by the sensor are balanced with the gravity of the test object. This is a zero gravity simulator.

Further, the present invention is characterized in that the control means performs dynamic external force compensation.

Further, the present invention is characterized in that it includes a speed detection means for determining the speed of the test object, and the control means performs feedforward control in response to the output of the speed detection means.

Operation According to the present invention, the gravity of an object attached to the tip of at least the active six-degree-of-freedom motion machine 1 (for example, the six-degree-of-freedom mouth hot arm) is canceled, and the equivalent inertial mass and equivalent moment of inertia at the tip of the active motion mechanism are canceled. By applying control to make 1~ as small as possible, it is possible to easily realize the movement of an attached object as if it were floating in a weightless space.

In other words, the basic idea of the present invention is to attach a force/torque sensor between the object whose weightless motion is to be simulated and the attachment section at the tip of the active 6-degree-of-freedom movement mechanism, and to constantly apply the sensor force to the object under test. The idea is to control the active movement mechanism so that it balances with gravity.

Embodiment FIG. 1 is a simplified cross-sectional view of one embodiment of the present invention. An active drive mechanism 2 such as an industrial robot is provided on the ground 1, and a test object 4 is attached to the active drive mechanism 2 via a sensor 3.

The sensor 3 detects force and torque acting on the test object 4. Gravitational acceleration is indicated by reference G.

The sensor 3 detects the force in each of the orthogonal X, Y, and Z axes, and also detects the torque around each of the X, Y, and Z axes. The active drive mechanism 2 with six degrees of freedom is, for example, x
, y, and z, and roll, pitch, and yaw attitudes about these axes to actively drive the object 4.

In order to facilitate understanding of the configuration for simulating zero gravity in three dimensions according to the present invention, firstly, with reference to FIG. The basic idea of the invention will be explained using one degree of freedom motion. The mass of the object 4 is Mp, the active 1-degree-of-freedom movement mechanism 2a
Let the mass of be Mq. It is assumed that the external force acting on the object is Fe, the force acting on the object via the force sensor 3 is FT, and its reaction force is (-FT). In addition, the active one-degree-of-freedom movement mechanism 2a
Let τ be the driving force that drives the object 4, and let Xp be the displacement of the object 4.

Zero-gravity motion (J) refers to the motion of an object 4 with mass Mp or Newton (Neu+ton) in response to an external force Fe.
) equation of motion, Mp xp=Fe ・
... (1) (... is the second derivative of time).

However, the equation of motion of the object 4 attached to the side 2a of the active one-degree-of-freedom motion machine is as follows.

Mp −xp=Fe+Fr
...(2) Mq -xp=τ-FT
...(3) Add the second and third equations, (Mp+Mq) xp=Fe+z+
・ (4) There is a case where τ30 is simply attached to a passive motion mechanism, and in that case, the mass changes to (Mp + Mq), which does not represent the mass Mp of the object 4 itself. Recognize.

Therefore, consider configuring a control system that uses the signal F of the force sensor 3 to change the driving force τ and actively move the drive mechanism 2a, thereby eliminating the influence of MCI as much as possible.

In other words, the driving force τ input to the active drive mechanism 2a is
τ−-gd FT through the control compensator gd in the figure.

... Constructed as (5).

If τ and F are eliminated from the second, third, and fifth equations, the following equations are obtained.

The sixth equation shows that if the gain of the control compensator gd is sufficiently large,
This approximately expresses the motion of the first equation.

That is, by feedback-controlling the output FT of the sensor 3, the mass Mq of the one-degree-of-freedom movement mechanism 28 can be made almost negligible.

In particular, if the configuration of the compensator gd allows FT to quickly converge to zero, except for the response at the moment of collision, the motion after contact will be an unrestrained (weightless) motion of the object 4 in the direction of the xp force. That will happen.

As an example of the configuration of such a control compensator gd, P, 1.1. Consider a D (proportional, integral, integral, differential) type compensator. At this time, the transfer function expression becomes (Kv, Kp, K, 1.K, ≧0). This actual configuration diagram is as shown in Figure 3.
Kp is the constant term 5, s+ is the differentiator 6, and K, ,
, 2 and Kvl are coefficient units 7 and 8 that multiply the constant term.
．． 9, 1/S indicates an integrator 10.11, and a subtracter 12 and an adder]3 are also provided.

By eliminating Xp and τ from the second, third, fifth, and seventh equations and constructing the transfer function G(s> from Fe to F, then from Mq, Mp>O, K, When 2=O, G(s> becomes a stable transfer function.

Also, when Kx2〉0, [Mq+ (1+Kp)・Mpl・K1□・Mp−M
If the gain parameter is adjusted to pKv−KI2·Ml)>0 (9), a stable third-order lag system will be obtained. This gd configuration includes P, I type, P, and D type configurations, which reduce the corresponding portion of the constant gain to O
This can be achieved by simply doing so.

It can be seen from the above that unconstrained motion of an object in one degree of freedom can be realized. The following describes a configuration in which the object 4 simulates weightless motion in space.

FIG. 4 is a schematic diagram when an external force Fe acts on an object in zero gravity space. It is assumed that the orthogonal coordinate system fixed to the test object 4 is Σ9, and the vector and tensor expressions of this coordinate system are given a subscript p on the upper right shoulder. In addition, the fixed coordinate system in which the active 6-degree-of-freedom motion mechanism is installed is Σ0,
The vector and tensor representations of this coordinate system are assumed to have a subscript 0 on the upper right shoulder.

An object is floating in weightless space, and an external force Fe is applied to this object.
, the motion is Newton Euler (
Neu+ton −Euler) equation, it is expressed as follows. d/dt represents time differentiation.

Here, Vp is the translational velocity vector of the center of mass of the object (C
I'), ωp is the angular velocity vector (ER3) of object 4, M
p is the mass of the object 4, Hp is the inertia tensor (3 rows and 3 columns) of the object 4, and 2e is the vector (ER3) from the center of mass of the object to the point of application of external force.

Equations 10 and 11 are vector equations that hold true in any coordinate system, but when both sides are expressed in the Σ0 system and summarized, the following is obtained by performing matrix-vector expression.

However, ωpp−−[ωpp]
-(14)t means t, and Top indicates a coordinate transformation matrix (orthogonal 3 rows and 3 columns) from the Σp system to the Σ0 system (x is a vector cross product symbol).

That is, the motion of the object 4 expressed by Equation 12 is the motion desired to be realized in the ground simulation test, and the goal to be achieved by the present invention is to realize a motion close to Equation 12.

Now, on the second floor, this test object 4 must be attached to the active 6-degree-of-freedom mechanism and the test must be carried out.
The figure is a schematic diagram without showing external forces acting on an object 4 suspended via an active drive mechanism 2 on the ground, ie in a gravitational field. This will be explained with reference to FIG.

First, consider the motion of the active six-degree-of-freedom mechanism 2. The mounting of the test object 4 in the active six-degree-of-freedom machine [2
IR3) It is known that the equation of motion of an active six-degree-of-freedom motion mechanism is as follows. Here, nq is the inertia matrix (6 rows and 6 columns) of the active 6-degree-of-freedom mechanism, fq (q・q) is its centrifugal Coriolis ring (6-dimensional vector), G (q) is the gravitational term (6-dimensional vector), τ is the generalized force input to each drive actuator of the active six degrees of freedom mechanism, tJ q
is the transposed matrix (6 rows and 6 columns) of the Jacobian matrix (representation of the Σ system) of the position of the point where the object is attached to the active 6-degree-of-freedom mechanism. Further, q, q, and q represent the displacement, velocity, and acceleration of each active actuator, and are six-dimensional vectors (here, . is the ]-time differential, and . . . is the 2-time differential of time).

Furthermore, considering the equation of motion of the object under test 4, as shown in Figure 5, when the active 6-degree-of-freedom motion mechanism is mounted, external forces and external moments F, , NT act from a point, so Equation 12 is The difference is as follows.

In the equation, a is a solid 1 hel from the center of mass of the object to be tested to the point at which the active drive mechanism is attached, and g is the gravitational acceleration vector. That is, the object under test attached to the active drive mechanism performs a motion governed by Equations 15 and 16, which is different from Equation 12, which is zero gravity.

This is similar to the simple one-degree-of-freedom motion, and the first
It is not the motion of the equation, but is an extension of the motion governed by the second and third equations to spatial motion. Now, just as we derived the fourth equation from the second and third equations, the first
Transform Equations 5 and 16.

As shown in Figure 5, the object under test 4 and the active drive! Attachment 2 sets the translational speed of the point to V? , assuming that the angular velocity of the attachment point is the same as that of the test object 4, Vr'-Vp0+ω
p'X at' - (17
)ω,. −ω1〕0
...(18) When formulas 17 and 18 are divided into one aircraft per time and the relationship of acceleration is derived, VTO coVll10-1-ωp OX a , O+ωp
OX a, O... (19) 0"°-"0°
...(20) By the way,
Since the displacement speed q of each actuator of the active 6-degree-of-freedom mechanism 2 and its mounting are naturally related to the translational velocity and angular velocity of a point, Jq is the Jacobian matrix of the active 6-degree-of-freedom mechanism, and the first
This is the same matrix that appears in Equation 5.

If we divide both sides of Equation 21 into one aircraft and derive the acceleration relationship, we get
It will look like below.

It is assumed that within the movable range that simulates weightless motion of the test object 4, the active 6-degree-of-freedom motion mechanism does not pass through the singularity of the mechanism, and the Jacobian matrix J q is regular. At this time, from Equation 22 (-1 represents the inverse matrix), 4-J, - ((ヰ)-J,
・q) 0 pieces...(23) Substituting the 23rd formula into the 15th formula, the 19th formula and the 20th formula
From the relationship in the formula, ■7 and ω are expressed as ωP and VP,
It will look like this:

However, here And so. Mana E is an identity matrix with 3 rows and 3 columns.

Also, the part [IR A'×] in formula 16 is also A. Use■5 If you rephrase it, From equations 24 and 27, F.

Then, the test object 4 is attached to the active 6 degrees of freedom mechanism, and the 28th equation is input to each actuator of the active 6 degrees of freedom mechanism 2. This is an equation of motion when τ acts and an external force Fe acts on the test object 4, and corresponds to the fourth equation of a simple one-degree-of-freedom mechanism.

If the input τ of each actuator is determined so that the 28th equation expresses exactly the same equation as the 12th equation, then the test object 4
This means that weightless motion has been achieved.

FIG. 6 is a block diagram of a simulator that simulates weightless motion using displacement information of each axis of the six-degree-of-freedom active drive mechanism 2 and information from the force/torque sensor 3 provided at its tip. In this FIG. 6, a diagonal control compensator 1 arranged in 6 rows and 6 columns
5, 6 rows and 6 columns product calculation circuits 16, 17, 18, 6 rows and 6 columns transposed Jacobian matrix product calculation circuit 19, 6 rows and 6 columns transposed Jacobian matrix product calculation circuit 20, and adder circuits 21 and 22.
゜23 is provided.

Comparing the 12th equation and the 28th equation, the condition that the two equations are equal is the following equation.

Simplifying Equation 29, we can therefore convert the output τ of the active six-degree-of-freedom drive mechanism into the static force τS
and the dynamic force τ. The sum of τ = τ + τD) is used in Equation 31.

That is, the static force τS and the dynamic force τ in Equation 31.

If it is possible to input ideally, the motion of the 28th formula will realize the target motion of the 12th formula.

However, since the input dynamic force τ is a dynamic feedforward type that includes acceleration, it is difficult to realize this.

Therefore, the static force τS is compensated by feedforward calculation and the dynamic force τ is calculated. proposes a method of compensation using feedback compensation from the force detector (force/torque sensor) 3.

FIG. 7 is a block diagram showing an embodiment in which a nonlinear velocity feedforward 5 is further added to the configuration diagram of the weightless motion simulator shown in FIG. 6. 6 rows 6
A product calculation circuit 25 for time integration of a column Jacobs matrix, a product calculation circuit 26 for a 6-by-6 inverse Jacobs matrix, a product calculation circuit 27 for a 6-row and 6-column inertia matrix, and addition circuits 28 and 29 are provided. .

Configure τ0 as follows.

In Equation 34, FA and NT can detect the attachment of the active 6-degree-of-freedom drive mechanism 2 and the test object 4 from the force/torque sensor 3 installed in the part, and GF is the control compensator (
6 rows and 6 columns).

By the way, considering the equation of Equation 16, this Equation 34 becomes
It can be expressed as follows.

Therefore, the static force τS in Equation 31 and the dynamic feedback τ in Equation 34. When applying, the equation obtained by substituting equations 31 and 35 into equation 28 becomes the equation that governs the test object. By substituting Equations 31 and 35 into Equation 28 and eliminating τ, the following equation is derived.

tυ Equation 36 corresponds to Equation 6 in the simple case of one degree of freedom, and if the gain of control compensator GF is sufficiently large, the third
The left side of Equation 6 has relatively little influence, and the motion approaches the motion of Equation 12.

Instead of the control compensator GF, a new control compensator G (6×6) is defined using the following equation.

At this time, GF's G. GD is a compensation element with 6 rows and 6 columns, but its simplest configuration is as shown in Equation 7, where only the diagonal components are P, 1.1.
It is sufficient to use a D-type compensator. Furthermore, G. By adding a compensation element to the off-diagonal components of G, we can create a compensator G with even better characteristics.
It is also possible to configure D.

The controller in Figure 6 above based on Equation 31 and Equation 3.1
- In the configuration of the roller, the center of mass of the test object in the figure and the attachment point of the active 6-degree-of-freedom motion mechanism are the constant matrix determined by J. tJq is the active 6-degree-of-freedom motion Because it is a transposed Jacobs matrix of the mechanism, the components of the matrix change from time to time, so calculations and updates are performed by the Microphone LTI computer.

Broken line part in Figure 6] 4 is the 31st formula, so S and 34th 2nd T
This is the basic configuration using 4.

Next, we will give an example of a more advanced configuration. This is the case when the velocity q of the active six-degree-of-freedom motion mechanism can also be detected, or (
This is an effective method when a pseudo-differential q can be generated from 1 and q can be used as information. Since q is detected, the following input is added as a new input fF.

That is, as the input τ of the active six-degree-of-freedom motion mechanism, τ=
τS+τD×τF
...Consider (41). When this compensation is performed, the term related to speed on the left side of Equation 36 disappears,
It will look like this:

τ corresponds to adding one foot-feed term of nonlinear velocity, and the response becomes sloppy, but it is useful for calculation of the inverse Jacobian matrix (=Jq-') and active six-degree-of-freedom motion mechanism. The burden of calculations such as calculation of the inertia matrix IIq increases.

However, it is quite possible to add a microcomputer, and the configuration diagram thereof is shown in the above-mentioned FIG. 7.

In order to simulate the weightless motion of the test object, it is attached to an active 6-degree-of-freedom motion mechanism, and its attachment is performed using a point force/
) A zero-gravity motion simulator can be constructed by feedback-controlling the torque.

In the present invention, there are two configurations: one that uses only the displacement of the active drive mechanism and the force/torque of the force detector, and another that uses speed information of the active drive mechanism.

Effects of the Invention As described above, according to the present invention, a test object is taken into an active drive mechanism such as a robot 1 having at least six degrees of freedom via a sensor that detects force and torque. Since the force and torque detected by this sensor are fed back to the active drive mechanism so as to balance the gravity of the test object, it is possible to realize a zero gravity state of the object in three dimensions relatively easily and in real time. It is possible.

Furthermore, according to the present invention, the control means performs dynamic external force compensation, detects the speed of the test object, and performs feedforward control based on the output of the speed detection means, thereby achieving high accuracy. It becomes possible to realize a state of zero gravity.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an outline of a zero gravity simulating device according to an embodiment of the present invention, FIG. 2 is a view showing a degree of freedom motion mechanism 2a with an object 4 attached, and FIG. 3 is a configuration of a compensator gd. 4 is a schematic diagram of an external force Fe acting on an object in zero gravity space, and FIG. 5 is a schematic diagram of an external force acting on an object 4 suspended via an active drive mechanism 2 in a gravitational field on the ground. FIG. 6 is a block diagram showing the configuration of a zero-gravity motion simulating device using displacement information of each axis of the six-degree-of-freedom active drive mechanism 2 and information from the sensor 3. FIG. FIG. 2 is a block diagram showing a configuration in which a nonlinear velocity feedforward term is added in an embodiment. 1... Earth, 2, 2a... Active drive mechanism, 3...
Sensor, 4... Gravity Agent Patent Attorney Stroke Number Keiichi

Claims (3)

[Claims] (1) an active drive mechanism that divides the test object into at least six degrees of freedom; a sensor that is interposed between the active drive mechanism of the test object and detects the force and torque acting on the test object; and the sensor and means for feedback controlling an active drive mechanism in response to the output of the sensor so that the force and torque detected by the sensor are balanced with the gravity of the test object. (2) The weightless simulator according to claim 1, wherein the control means performs dynamic external force compensation. (3) A speed detecting means for determining the speed of the test object is provided, and the control means performs feed forward control in response to the output of the speed detecting means. Zero gravity simulator.