JP4982413B2 - Leg wheel type mobile robot - Google Patents

Description

  The present invention relates to a standing motion of a legged mobile robot having wheels at its leg tips.

  There is a method using ZMP (ZeRo Moment Point) and a support convex polygon as a method for determining a fall in various robots. ZMP is the center of drag at the contact point, and is the point on the floor where the moment due to drag is zero. The supporting convex polygon is a minimum convex polygon that includes a portion where the robot is grounded and can be loaded. When the ZMP is inside the support convex polygon except on the side, the robot does not fall down and moves by driving the legs and wheels while keeping the ZMP in the support convex polygon. I can do it.

  Patent Documents 1 and 2 and Non-Patent Document 1 are known as performing a bipedal operation by ZMP.

  In a robot that supports its own weight by a multi-link mechanism as shown in these Patent Documents 1 and 2 and Non-Patent Document 1, the degree of freedom of the legs is used when moving, thereby overcoming road surface irregularities, steps, and grooves. Is expensive. However, if the inter-link angle of the multi-link mechanism is not always controlled, there is a problem that energy must always be spent for maintaining the posture because the ZMP reaches the side of the support convex polygon and falls. For this reason, while not controlling the angle between the links, it is necessary to take a posture different from that at the time of movement or to maintain the posture by limiting the degree of freedom of the legs by using an auxiliary tool.

JP-A-5-305579 JP 2001-138272 A OHM "Humanoid Robot" ISBN4-274-20058-2

  Bend the legs as a posture in the middle of returning after a robot with two legs falls down, or place the ZMP in a support convex polygon without controlling each joint during standby, and ground from the standing posture Suppose you take a waiting posture with more parts. In order to take a standing posture by extending the legs from this standby posture, the conventional robot tilts the upper body, moves the ZMP to a common supporting convex polygon in the standing posture and the standby posture, and then ZMP supports the convex convex polygon. There is a technique to take a standing posture by extending the legs so that they do not come off. In addition, when the robot is tilted to the left or right and the ZMP is placed in the support convex polygon formed by only one leg, the other leg is moved, the tilt of the robot is removed, and the ZMP is returned to the center of the left and right. The leg is extended from the stand-by posture to fit within the common support convex polygon, then the leg is extended so that the ZMP does not deviate from the support convex polygon, and the standing posture is obtained by aligning the legs. There is.

  However, in the former method, when the length of the upper link and the lower link of the leg are greatly different, the upper body weight is not enough, the center of gravity of the upper body is greatly separated from the supporting convex polygon, such as carrying luggage, etc. In order to fit the ZMP in the support convex polygon by tilting the upper body in the front-rear direction, it is necessary to tilt the upper body greatly, which may be restricted by the range of movement of the robot or may collide with the surroundings by tilting greatly There are problems such as sexuality. In the latter method, since it is necessary to store the ZMP in the support convex polygon formed by only one leg, the area of the support convex polygon cannot be increased, and there is a risk of falling due to disturbance. In addition, when it is necessary to keep the upper body of the robot horizontal, it is necessary to add a rotary joint to cancel the inclination of the upper body, and there is a problem that the mechanism becomes complicated.

  The object of the present invention is to stably transition from a stand-by posture in which a foot is bent, a wheel and a leg are grounded and a supporting convex polygon is made large, to a standing posture in which the leg is extended and has a large degree of freedom regarding movement. The object is to provide a robot apparatus capable of performing the above.

The object is to provide two legs having a plurality of links and a plurality of joints for connecting the links so as to bend, and a body part connected to one end of the two legs via the joints. A leg wheel type mobile robot comprising a wheel provided to rotate at the other end of each leg, and a control means for controlling the operation of the leg and the wheel, wherein the control means comprises the leg The one of the two legs is moved in the advancing direction of the wheel while maintaining the grounding of the wheel from the posture in which the joint and the leg are grounded by bending the joint provided in the wheel, If the leg wheel type mobile robot has a control means for controlling so that only the wheel of the leg touches the ground, and the center of gravity of the leg wheel type mobile robot is not between the two wheels, three or more points are grounded It is one cause, the control The stage includes a step in which all the wheels are grounded, a step in which one side of the leg is sent forward while the ZMP is inside the support convex polygon, and the ZMP is sufficiently close to a line segment formed by the wheel ground point. This is achieved by performing a control including a control step and a step of shifting to an inverted state .

  Further, the object is that the control means bends the plurality of joints provided on the two legs, and makes one of the legs contact the ground of the wheel from a posture in which the wheel and the two legs are grounded. The two wheels are moved in the traveling direction while maintaining the position so that only the wheels of the two legs are in contact with the ground, and then the plurality of joints provided on the two legs are extended to the two legs. This is achieved by providing a control means for controlling the operation.

  According to the present invention, from a standby posture in which a part of the wheel and the leg is grounded and the support convex polygon is made large, the standing posture having a high degree of freedom regarding movement regardless of the weight balance of the upper body and the inclination angle limitation of the upper body It is possible to provide a leg-wheel type mobile robot capable of performing a stable posture change.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a leg-wheel type mobile robot provided with an embodiment of the present invention.
FIG. 2 is a diagram showing a joint arrangement of a leg-wheel type mobile robot provided with an embodiment of the present invention.
1 and 2, the front direction of the robot is the X axis, the side surface direction is the Y axis, and the vertical direction is the Z axis. The robot 1 is mainly composed of a leg portion 10 and a trunk portion 100. The leg portion 10 is composed of left and right legs 11R, 11L, each of which includes thigh portions 12R, 12L, lower limb portions 13R, 13L, and wheels 14R, 14L. The torso 100 has a torso 101 positioned above the left and right legs 11R, 11L, a control device 110 that controls the operation of all joints and wheels, which will be described later, and an inclination angle Ψ and an angular velocity dΨ / dt with respect to the direction of gravity of the torso. The tilt angle detection device 111 to be detected and the left and right arms 120R and 120L, the arms (left and right) 120R and 120L include the upper arms 121R and 121L, the lower arms 122R and 122L, and the hands 123R and 123L.

  When it is necessary to distinguish between these legs or arms, “R” is added to the end of the Y-axis positive direction, and “L” is added to the end of the Y-axis negative direction. Between the thighs 12R, 12L and the torso 100, the rotary joints 20R, 20L centering on the Y axis are between the thighs 12R, 12L and the lower limbs 13R, 13L. Rotating joints 21R and 21L are provided as central axes. Below the lower limb portions 13R and 13L, wheels 14R and 14L are provided at wheel rotary joints 22R and 22L having the Y-axis direction as a central axis. Between the trunk 101 and the upper arms 121R and 121L, rotary joints 30R and 30L having the X-axis direction as the central axis and rotary joints 31R and 31L having the Y-axis direction as the central axis are provided. Between the upper arms 121R and 121L and the lower arms 122R and 122L, rotary joints 32R and 32L having the Y-axis direction as a central axis are provided. Further, a motor having an angle detection function is attached to all the joints and wheels, and a torque τ specified by the control device 110 can be generated.

  The robot 1 according to the present embodiment takes a standing posture that is a posture in which only the wheels 14R and 14L are grounded during movement. In this position, coaxial two-wheel inverted pendulum control is performed. In the inverted pendulum control, the control device 110 obtains information on the tilt angle ψ, angular velocity dψ / dt with respect to the direction of gravity of the fuselage from the tilt angle detection device 111, and information on the wheel rotation angle and wheel rotation angular velocity from the wheels 14R, 14L. Move while maintaining. In order not to move, the robot 1 bent the thighs 12R, 12L and the lower limbs 13R, 13L and grounded the wheels 14R, 14L and a part of the lower limbs 13R, 13L in order to improve stability when not moving. Take a posture. In this posture, the supporting convex polygon can be made large. This is hereinafter referred to as a standby posture.

Next, a method for calculating ZMP in the control device 110 will be described. The control device 110 receives as input the angle and angular velocity information of all the joints provided in the robot 1 and the tilt angle and angular velocity with respect to the direction of gravity of the body 101 obtained from the tilt angle detecting device 111. By using these, the position of the center of gravity of the whole body can be calculated, and there are various methods, for example, the method described in Non-Patent Document 1. The relationship between the calculated center-of-gravity position vector of the whole body on the XY plane, G _xy , the Z-axis direction G _h , and the mass of the robot 1 M, is the gravity of the ZMP position Z _xy on the floor surface. It is expressed by the following equation using a constant g.

  FIG. 3 is a diagram showing a posture change from the standby posture (S1) to the standing posture (S4, S5) by the leg-wheel type mobile robot provided with an embodiment of the present invention.

  In FIG. 3, S1 is a standby posture in which the thighs 12R, 12L and the lower limbs 13R, 13L are bent and the wheels 14R, 14L and a part of the lower limbs 13R, 13L are grounded, and S2 is a leg posture. S3 is a posture in which one side can be sent in the wheel traveling direction, S3 is a posture in which the ZMP is located on a line segment with both ends of the grounding points of the wheels 14R and 14L, and S4 is a posture in which only the wheels 14R and 14L are grounded. S5 is a standing posture in which two legs are advanced and the left and right are aligned. The robot 1 of this embodiment stands up through the above procedure.

First, a method for calculating ZMP will be described. The radius of the wheels 14R, 14L is w, the distance between the ground and the joint 20R in the standby posture is R1, the length of the thigh 12R is u, the length of the lower limb 13R is d, and the angle θ _{20 of the} joints 20, 21 , Θ ₂₁ . The joint angles θ ₂₀ and θ ₂₁ are defined as a right-hand thread relationship in the Y-axis direction with reference to the case where the torso 101, the thigh 12 and the lower limb 13 are in a straight line.

  First, the posture is set to a standby state (S1) in which the wheels 14R and 14L and a part of the lower limbs 13R and 13L are grounded. From this state, the procedure to the posture (S3) in which the right leg 11R is moved back and forth in the wheel traveling direction and the ZMP is brought on the line segment having the ground contact points of the wheels 14R and 14L as both ends will be described. In order to send out one leg from the standby state in the wheel traveling direction, Equation 2 must be established from the geometric condition.

  In Equation 2, the left and right joints are not distinguished, so the R and L subscripts are omitted. When Expression 2 is not satisfied in the standby state (S1), the joints 21R and 21L are extended equally to satisfy the condition of Expression 2. At the same time, the control device 110 controls the ZMP so that it fits within the support convex polygon formed by both legs. In this embodiment, the joints 21R and 21L are extended so as to minimize R1 (S2).

Let A be the distance in the X direction from the joint 21R to the wheel 14R in the posture (S2) in which the joint 21 is extended so that Formula 2 is established. The control device 110 moves the right leg 11R by A in the front-rear direction while maintaining the installation of the wheel 14R, and controls the ZMP to be in a posture (S3) positioned on a line segment with both ends of the ground contact points of the wheels 14R and 14L. To do. At this time, the joint angles θ ₂₀ R and θ ₂₁ R have the relationship of Equation 3 when the wheel front-rear direction movement amount A is used. The movement pattern of the joint angles θ ₂₀ R and θ ₂₁ R is obtained by continuously changing the wheel longitudinal movement amount A and numerically solving Equation 3, and according to this movement pattern, the control device 110 causes the joints 20R, 21L. To control. At this time, since the heights of the joints 20R and 20L from the ground are constant, the left and right inclination of the trunk portion 100 is maintained.

  As described above, it is possible to reduce the risk of falling even during posture change by always grounding at least three points and taking a large support convex polygon.

  The standing posture in which only the wheels 14R, 14L are grounded from the posture (S3) in which the wheels 14R, 14L and the lower limbs 14L are grounded and the ZMP is located on the line segment having the grounding points of the wheels 14R, 14L as both ends. The posture change to (S4) changes when the control device 110 performs the inverted pendulum control by applying the torque τ expressed by Formula 4 to the wheels 14R and 14L.

  Here, Ψ is an average of the rotation angles of the wheels 14R and 14L, dΨ / dt is a time derivative thereof, and τ is a wheel driving torque generated by the wheel rotation joints 22R and 22L. The average rotation angle Ψ of the wheels 14R and 14L is set to 0 immediately before performing the inverted pendulum control. K is a control gain represented by a vector, which can be obtained by a known method, for example, Japanese Patent Laid-Open No. 63-305082.

  The posture change from the posture (S4) in which only the wheels 14R and 14L are grounded to the posture (S5) in which only the wheels 14R and 14L are grounded and the legs are extended to perform the coaxial two-wheel inverted pendulum control will be described. The joints 21R and 21L are extended, and then the indirect 20R and 20L are moved to align the left and right wheels 14R and 14L. At this time, since the stability in the front-rear direction is guaranteed by the inverted pendulum control, the motion pattern of the joint angles of the legs is arbitrary for the torque, rotation angle, and rotation angular velocity limitations, and the leg development and left-right alignment are performed simultaneously. Also good.

  By operating in accordance with the above procedure, the posture can be changed stably from the standby posture in which the leg is folded and the supporting polygon is made larger to the standing posture in which the leg is extended.

  The above description mainly uses the right leg 11R, but the same applies to the case where the left leg is used. Further, in this embodiment, since there is no rotational joint in the direction with the X axis as the central axis, the left and right inclination of the body 101 is constant, but a directional rotational joint with the X axis as the central axis is added to support the ZMP. The body 101 may be arbitrarily inclined within a range that remains in a convex polygon. If the ZMP can be held within the support convex polygon in the stand-by posture even when the arms (left and right) 120R, 120L are held, take the same procedure after including the effects of the load on the ZMP. Thus, the posture change from the standby posture to the standing posture can be performed stably.

It is the schematic about the robot of one Example of this invention. It is a figure which shows the joint structure in the robot of one Example of this invention. It is a figure showing the attitude | position change from the stand-by attitude | position to the standing attitude | position in the robot of one Example of this invention.

Explanation of symbols

1 Robot 10 Leg 11R, 11L Leg (left and right)
12R, 12L Thigh 13R, 13L Lower limb 14R, 14L Wheel 100 Body 101 Body
110 Control device 111 Inclination angle detection device 120R, 120L Arm (left and right)
121R, 121L Upper arm 122R, 122L Lower arm 123R, 123L Hand

Claims (2)

Two legs provided with a plurality of links and a plurality of joints connected so as to bend and drive the links; a body part connected to one end of the two legs via the joints; In a leg-wheel type mobile robot provided with wheels provided so as to be rotationally driven at each other end, and a control means for controlling the operation of the legs and the wheels,
The control means is configured to bend the joints provided on the legs so that one of the two legs is kept in contact with the wheel and one of the two legs from a posture in which the legs are grounded. Control means for controlling so that only the wheels of the two legs are in contact with the ground,
When the center of gravity of the leg wheel type mobile robot is not between the two wheels in the leg wheel type mobile robot, three or more points are grounded ,
The control means includes
All the wheels are grounded;
Sending one side of the leg forward while ZMP is inside the support convex polygon;
A process of controlling the ZMP so that it is sufficiently close to the line segment formed by the wheel contact point;
A leg-wheel type mobile robot characterized by performing control including a step of shifting to an inverted state . The leg-wheel type mobile robot according to claim 1,
The control means bends the plurality of joints provided on the two legs, the wheel and the 2
One of the legs is moved in the advancing direction of the wheel while maintaining the grounding of the wheel from a posture in which the leg is grounded, and only the wheel of the two legs is grounded, and then the 2 A leg-wheel type mobile robot comprising control means for controlling the plurality of joints provided on a leg so as to extend the two legs.

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