JP4078857B2 - Legs of legged mobile robot and legged mobile robot - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a legged mobile robot having a plurality of movable legs, and more particularly to a foot structure that is provided at the tip of the movable legs and comes into contact with a floor surface during a walking motion.
[0002]
[Prior art]
In recent years, research and development on legged mobile robots imitating animals that walk biped upright, such as humans and monkeys, have progressed, and expectations for practical use are also increasing. A legged mobile robot with two legs standing upright is more unstable than a crawler or four-legged or six-legged robot, and posture control and walking control are complicated, but the walking surface has irregularities on the work path. It is excellent in that it can realize flexible moving work, such as being able to cope with discontinuous walking surfaces such as stairs and ladders (such as rough terrain and obstacles).
[0003]
Most of the human work space and living space are formed according to the human body's physical mechanism and behavioral style of standing upright with two legs. In other words, the human living space has too many barriers for the current mechanical system that uses wheels or other drive devices as moving means to move. In order for a mechanical system, that is, a robot to support or substitute for various human tasks and further penetrate deeply into a human living space, it is preferable that the movable range of the robot is substantially the same as that of a human. This is why the practical application of legged mobile robots is highly expected. It can be said that having a humanoid form is indispensable for a robot to enhance its affinity with a human living environment.
[0004]
Many techniques relating to posture control and stable walking have already been proposed for robots that perform legged movements by biped walking. Many of them use ZMP (Zero Moment Point) as a norm for determining the stability of walking. According to the ZMP stability criterion, gravity, inertial force, and these moments act on the road surface from the walking system, and this balances the floor reaction force and floor reaction force moment as a reaction from the road surface to the walking system. Based on D'Alembert principle. As a result of mechanical reasoning, there is a point where the pitch and roll axis moment become zero on or inside the side of the support polygon formed by the contact point of the sole and the road surface, and this point is called ZMP.
[0005]
Biped walking control based on the ZMP norm has advantages such that a foot landing point can be determined in advance, and it is easy to consider the kinematic constraint conditions of the foot according to the road surface shape. In addition, using ZMP as a stability determination criterion means that a trajectory, not a force, is treated as a target value in motion control, and thus technical feasibility increases. Regarding the concept of ZMP and the application of ZMP to the stability criteria for walking robots, Migir Vukobratovic's “LEGGED LOCATION ROBOTS” (Ichiro Kato's “Walking Robots and Artificial Feet” (Nikkan Kogyo Shimbun)) It is described in.
[0006]
When performing robot motion control using ZMP as a stability criterion, it is very effective to measure actual ZMP. For this reason, a plurality of sensors for detecting ZMP, such as force sensors, are disposed on the foot provided at the tip of the movable leg of the robot. The detection values of these sensors are A / D converted and taken into the main control unit provided in the robot body, and the main control unit calculates the actual ZMP based on these detection values, and performs the walking motion of the robot. It is used for the control of each part.
[0007]
As the installation position of the ZMP detection sensor, for example, when adopting a double structure in which a foot part is composed of a foot member and a sole member that is movably attached to the foot member, the foot member and the In general, it is interposed between the sole member and the sole member in a preloaded state.
[0008]
[Problems to be solved by the invention]
However, according to the conventional foot structure, since the ZMP detection sensor is provided in a pre-loaded state between the instep member and the sole member, each sensor is calibrated (zero point adjustment). There is a problem in that it is necessary to carry out the preload acting on the sensor so as to be an appropriate value within the detection range of each sensor, and the work is not easy.
[0009]
Further, when the sole member is replaced, it is necessary to perform the above operation every time, and there is a problem that the operation accompanying the replacement is complicated and the man-hour is large.
[0010]
The present invention has been made in view of such points, and the object of the present invention is to eliminate the need for preload adjustment work for calibration of the force sensor and to improve the accuracy of the detection value of the sensor. It is to reduce the work burden associated with the replacement of the sole member.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the leg of the legged mobile robot according to the first aspect of the present invention is a leg of a legged mobile robot provided with a movable leg, and an instep member attached to the tip of the movable leg. A sole member detachably attached to the instep member, four force sensors provided on one of the instep member and the sole member, and the other of the instep member and the sole member. When the sensor pressing member provided corresponding to each of the four force sensors and the sole member are not in contact with the road surface, the sensor pressing member is separated from the force sensor, and the sole member is grounded. The foot member and the sole member are biased so as to be separated from each other so that the sensor pressing member is pressed against the force sensor. four biasing member is, the instep member及And an electric circuit board to which a signal is transmitted from the plurality of force sensors with provided on one of said sole member, wherein the four force sensors, the four corners of the instep member or the sole member The four biasing members are arranged at positions between force sensors adjacent in the circumferential direction.
[0012]
In order to achieve the above object, a legged mobile robot according to the second aspect of the present invention includes the above-described leg according to the first aspect of the present invention.
[0013]
According to the present invention, when the sole member is not in contact with the road surface, the sensor pressing member is separated from the force sensor, that is, in a state in which no preload is applied, and when the sole member is in contact with the road surface, the force sensor Since the sensor pressing member is brought into pressure contact with the pressure sensor, there is no need for the work associated with the preload adjustment of each force sensor, which has been caused by preloading the force sensor as in the prior art.
[0014]
In addition, since the calibration of each force sensor can be performed in a state where the sensor pressing member is separated from the force sensor, that is, at the time of the swing leg, the calibration can be performed at a relatively short interval. The reliability of the detected value can be improved. Furthermore, as long as the relative positional relationship of each force sensor in the Z-axis direction (direction orthogonal to the sole surface) is set accurately, the relative positional relationship between the sole member and the force sensor can be changed when replacing the sole member. Therefore, the sole member can be easily replaced. In addition, since the impact from the sole member is not immediately transmitted to the force sensor, the impact resistance can be improved.
[0015]
In the present invention, although not particularly limited, it is desirable to provide the force sensor on the instep member and the sensor pressing member on the sole member. When the sensor is provided on the sole member, wiring connection work such as signal lines is required when replacing the sole member. However, by providing the sensor on the foot member side, such wiring connection work is required. This is because the work associated with the replacement can be facilitated. Further, when the sole member is configured to be able to move relative to the instep member, it is possible to eliminate damage to the wiring and obstruction of movement of the sole member due to the wiring.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 and FIG. 2 show a state in which the “humanoid” legged mobile robot 100 used for carrying out the present invention is viewed from the front (FIG. 1) and the rear (FIG. 2). Show. As shown in the figure, the legged mobile robot 100 is composed of left and right lower legs 110, trunk 120, left and right upper limbs 130, and a head 140 as movable legs that perform legged movement.
[0018]
Each of the left and right lower limbs 110 includes a thigh 111, a knee joint 112, a neck 113, an ankle 114, and a foot 150, and is connected by a hip joint 115 at a substantially lowermost end of the trunk 120. Yes. Each of the left and right upper limbs 130 includes an upper arm 131, an elbow joint 132, and a forearm 133, and is connected to the left and right side edges above the trunk 120 by shoulder joints 134. The head 140 is connected to the substantially uppermost center of the trunk 120 by a neck joint 141.
[0019]
In the following description, for convenience of description, in the description of the foot 150, a surface that includes a portion that contacts the road surface (floor surface) on the back surface of the foot 150 is referred to as an XY plane, and the XY plane. In the following description, it is assumed that the front-rear direction of the robot is the X axis, the left-right direction of the robot is the Y-axis, and the direction perpendicular to these is the Z-axis.
[0020]
Each joint is provided with an actuator. The operation of the robot is realized by driving the actuator. The joint actuator is small and lightweight due to various demands such as eliminating the extra bulge on the appearance of the device and approximating it to the natural shape of a human being, and performing posture control on an unstable structure called biped walking. It is preferable that For this reason, in the present embodiment, a small AC servo actuator of a type directly connected to the gear and having a servo control system in one chip and built in the motor unit is mounted. A small AC servo actuator applicable to a legged robot is disclosed in, for example, Japanese Patent Application No. 11-3386 already assigned to the present applicant.
[0021]
Inside the trunk 120, a main control unit, a power supply circuit, and other peripheral devices that are not visible in FIGS. 1 and 2 are mounted.
[0022]
FIG. 3 shows an outline of the configuration of the control system of the legged mobile robot 100. The main control unit (control means) 300 includes a CPU (Central Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303 in which operation patterns and the like are stored, and a legged mobile robot 100. Are provided with an A / D converter 305 for converting an analog signal as an output of various sensors 306 mounted on the digital signal into a digital signal, and these are connected to each other via a bus 304.
[0023]
The CPU 301 generates an operation of the legged mobile robot 100 based on information stored in the ROM 303 and outputs of various sensors 306, and determines a command value to the AC servo actuator 307 disposed at each joint.
[0024]
These AC servo actuators 307 are connected to the main control unit 300 via the bus 304 and can receive command values for the respective joints calculated by the CPU 301. The AC servo actuator 307 is operated according to this command value, and various operations including the walking motion of the legged mobile robot 100 are realized.
[0025]
Next, the structure of the foot 150 will be described. FIG. 4 is a cross-sectional view showing the structure of the foot portion according to the embodiment of the present invention, and FIG. 5 is a bottom view of the instep member. The foot 150 includes a toe member 1010 that is connected to the ankle 114 of each of the left and right lower limbs 110 and a sole member 1020 that is directly grounded to the road surface, and the sole member 1020 moves freely to the instep member 1010. It has a double structure that can be attached.
[0026]
The instep member 1010 is a substantially rectangular box-shaped member whose lower surface is opened, and has a substantially rectangular plate-shaped top plate portion 1011 and a side plate portion 1012 that is integrally provided along the periphery thereof. . A connecting portion 1013 for connecting to the ankle 114 is integrally provided on the top surface of the top plate portion 1011. Screw holes (four in this example) 1014 for attaching the sole member 1020 are formed in the top plate portion 1011. The boundary portion of the outer surface of each side plate portion 1012 is an R surface (arc surface) or a smooth curved surface.
[0027]
The instep member 1010 is attached to the ankle 114 by fixing the instep member 1010 to the ankle 114 using a screw or other fixing means, or although not shown, it can be attached and detached via a coupling mechanism. You may make it attach to. An electric circuit board 1100 is attached via a plurality of support members 1110 substantially at the center of the lower surface of the top plate portion 1011 of the instep member 1010.
[0028]
Convex sensor pedestals 1015 are integrally formed in the vicinity of the four corners on the lower surface of the top plate 1011 of the instep member 1010, and ZMP is calculated at the tip of the sensor pedestal 1015. A plurality of force sensors (for example, load cells) 1016 for detecting the pressure in the Z-axis direction are provided. Each of these force sensors 1016 includes a metal diaphragm and four strain gauges, and a bridge circuit is formed by the four strain gauges, and the strain gauges are attached to the metal diaphragm. However, the force sensor 1016 is not limited to such a configuration, and may have another configuration. In the present embodiment, the force sensor 1016 is of a type that can detect pressure with desired accuracy even without preload.
[0029]
A cable (here, a flexible cable) 1130 for supplying power to the force sensor 1016 and transmitting a signal from the force sensor 1016 is connected to the electric circuit board 1100. To connect the force sensor 1016 and the electric circuit board 1100 in the flexible cable 1130, unnecessary force to the force sensor 1016 by the cable tension in order to prevent the action. On the electric circuit board 1100, arithmetic processing means (CPU, ROM, RAM, etc.) 1120, an acceleration sensor 1140 for detecting acceleration in the X-axis direction and the Y-axis direction, and the like are also mounted. The output of the acceleration sensor 1140 is used to detect the inclination of the road surface with respect to the gravitational direction and to detect the rolling due to the road surface unevenness.
[0030]
The sole member 1020 is formed by attaching a grounding member 1022, which is also a substantially rectangular plate member, to the lower surface of the sole body 1021, which is a substantially rectangular plate member, and is integrally attached using screws or the like. It has a heavy structure.
[0031]
The outer shape of the sole main body 1021 is substantially the same shape as the outer shape of the side plate portion 1012 of the instep member 1010 on the opening side. On the upper surface of the sole body 1021, there are formed fixing protrusions 1024 that are convex upward corresponding to the screw holes 1014 formed in the top plate part 1011 for attachment to the instep member 1010. The lower side of the fixing projection 1024 is a recessed portion 1025 that is recessed in a columnar shape in order to insert a stepped bolt 1150 having a thread at its tip from the lower side. A through hole 1026 penetrating vertically is formed at the center of the tip of each fixing projection 1024. Further, a sensor pressing pedestal portion that presses or abuts against the force sensor 1016 at a position corresponding to each of the force sensors 1016 provided on the sensor pedestal portion 1015 of the top plate portion 1011 of the instep member 1010. (Sensor pressing members) 1027 are integrally formed.
[0032]
The grounding member 1022 has substantially the same shape as the outer shape of the sole body 1021, and through holes 1028 are formed corresponding to the recesses 1025 of the sole body 1021. The grounding member 1022 is formed of, for example, an elastic rubber sheet in order to reduce the impact when the foot 150 is grounded on the road surface. As a material of the ground contact member 1022, in addition to the rubber sheet, various materials such as metal, plastic, and the like can be adopted from the viewpoint of the road surface condition compatibility. From this point of view, it is possible to adopt a groove formed or a arch formed. By appropriately changing and selecting the material of the grounding member 1022 and the shape of the grounding surface, various types of sole members 1020 corresponding to various road surface conditions can be configured.
[0033]
A stepped bolt 1150 is inserted into the recess 1025 and the through hole 1026 of the sole member 1020 from below, and a coil spring 1160 is attached so that the stepped bolt 1150 penetrates the inside of the stepped bolt 1150. The sole member 1020 can be attached to the instep member 1010 by screwing the screw thread into the screw hole 1014 of the top plate portion 1011 to the limit (step surface). A cylindrical cushioning member (not shown) made of, for example, elastic rubber or a coil spring may be interposed between the ceiling portion of the recess 1025 and the head of the stepped bolt 1150.
[0034]
When the walking operation is started in a state where the foot portion having such a configuration is attached to the ankle of the leg of the robot, the foot portion is separated from the road surface at the time of the free leg, that is, the force from the road surface is applied to the sole member 1020. In the state in which no action is applied, the sole member 1020 is separated from the instep member 1010 to the stroke limit defined by the stepped bolt 1150 by the urging force of the coil spring 1160, and the top plate The force sensor 1016 attached to the sensor pedestal portion 1015 provided on the lower surface of the portion 1011 and the tip surface of the sensor pressing pedestal portion 1027 provided on the sole body 1020 face each other with a predetermined gap therebetween. ing. This gap is set to about 0.7 mm, for example.
[0035]
At the time of grounding, that is, in a state where the foot is grounded on the road surface and the force from the road surface is acting on the sole member 1020, the sole member 1020 resists the urging force of the coil spring 1160 and the instep member 1010. The tip surface of the sensor pressing pedestal portion 1027 provided on the sole body 1020 is pressed against the force sensor 1016 attached to the sensor pedestal portion 1015 provided on the lower surface of the top plate portion 1011, Pressure from the road surface is transmitted to the force sensor 1016. The output of the force sensor 1016 is sent to the arithmetic processing means 1120 on the electric circuit board 1100 via the cable 1130, and after necessary processing is transmitted to the main control unit 300 of the robot body, ZMP calculation processing is performed. Executed. In order to reduce the processing load on the main control unit 300 of the robot body, ZMP may be calculated by the foot calculation processing means 1120 and then transmitted to the main control unit 300 of the robot body.
[0036]
According to the present embodiment, a force sensor 1016 for detecting ZMP is a type that does not require preload, and when the sole member 1020 is not in contact with the road surface, the sensor pressing base portion from the force sensor 1016. 1027 is in a separated state, that is, in a state in which no preload is applied, and when the sole member 1020 comes in contact with the road surface, the sensor pressing base 1027 is pressed against the force sensor 1016, so it is necessary to adjust the preload. Is completely gone. In addition, since the coil spring 1160 that biases the sole member 1020 away from the instep member 1010 is interposed between the instep member 1010 and the sole member 1020, the occurrence of vibration of the sole member 1020 is small. Generation of noise can be reduced. Further, since the calibration of each force sensor 1016 can be performed in a state where no external force is applied to the sole member 1020, the calibration can be performed at the time of a swinging leg accompanying a walking motion, and an accurate detection value is always obtained. Be able to get.
[0037]
Further, the sole member 1020 can be easily replaced by removing the stepped bolt 1150, and at the time of assembly, the stepped bolt 1150 is screwed to the limit of screwing, so that the sole member 1020 is replaced with the instep member. A predetermined positional relationship with respect to 1010 can be easily set, and the replacement work is extremely easy.
[0038]
In addition, since the sole member 1010 is separated from the force sensor 1016 during the swinging leg, even if some kind of impact is applied to the sole member 1020, the impact is less likely to be transmitted to the force sensor 1016. Further, the damage of the force sensor 1016 can be reduced.
[0039]
The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment includes all design changes and equivalents belonging to the technical scope of the present invention.
[0040]
【The invention's effect】
According to the present invention, there is an effect that the preload adjustment work for calibration of the force sensor becomes unnecessary, and the detection value of the sensor can be made highly accurate. In addition, there is an effect that it is possible to reduce the work burden associated with the replacement of the sole member.
[Brief description of the drawings]
FIG. 1 is a perspective view of a legged mobile robot according to an embodiment of the present invention as viewed obliquely from the front.
FIG. 2 is a perspective view of the legged mobile robot according to the embodiment of the present invention as viewed obliquely from the rear.
FIG. 3 is a diagram showing a configuration of a control system of the legged mobile robot according to the embodiment of the present invention.
FIG. 4 is a side sectional view showing a configuration of a foot portion according to the embodiment of the present invention.
FIG. 5 is a bottom view of the instep member of the foot portion according to the embodiment of the present invention.
[Explanation of symbols]
150 ... Foot (foot)
300 ... Main control unit 1010 ... Instep member 1016 ... Force sensor 1020 ... Sole member 1027 ... Sensor pressing base 1100 ... Electric circuit board 1150 ... Stepped bolt,
1160 Coil spring

Claims (3)

In the legs of a legged mobile robot with movable legs,
An instep member attached to the tip of the movable leg;
A sole member detachably attached to the instep member;
Four force sensors provided on one of the instep member and the sole member;
A sensor pressing member provided corresponding to each of the four force sensors on the other of the instep member and the sole member;
When the sole member is not in contact with the road surface, the sensor pressing member is separated from the force sensor, and when the sole member is grounded, the sensor pressing member is in pressure contact with the force sensor. Four urging members interposed between the instep member and the sole member for urging the member and the sole member to be separated from each other;
An electric circuit board that is provided on one of the instep member and the sole member and that transmits signals from the plurality of force sensors;
Said four force sensors, the arranged four corners of the instep member or the sole member, wherein the four biasing member, characterized in that arranged at a position between the force sensor circumferentially adjacent Legs of legged mobile robot.   The leg of the legged mobile robot according to claim 1, wherein the force sensor is provided on the instep member and the sensor pressing member is provided on the sole member.   A legged mobile robot comprising the foot according to claim 1.

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