Patent ID: 12194619

DESCRIPTION OF EMBODIMENT

In the following, a mode for carrying out the present invention (hereinafter referred to as an embodiment) is described with reference to the drawings.

FIG.1is a schematic view of a humanoid robot2that is an embodiment of the legged mobile robot according to the present invention and depicts a perspective view of the humanoid robot2in a standing state. The humanoid robot2includes movable parts that enables movements similar to those of a human in addition to the legs. In particular, the humanoid robot2includes a body4, a head6, and a pair of left and right upper limbs8and a pair of left and right lower limbs10.

The body4is composed of a chest4uand an abdomen4d, and a relative angle between them can be changed around three axes for rolling, pitching, and yawing by an actuator group20.

The head6is connected over the chest4u, and an angle thereof can be changed around three axes for rolling, pitching, and yawing by an actuator group21provided at a connection portion corresponding to a neck joint.

Each of the left and right upper limbs8includes a first upper limb portion8s, a second upper limb portion8u, and a third upper limb portion8fwhich are connected in order from a side edge of the chest4u, and an actuator disposed at each connection portion thereof. The second upper limb portion8ucorresponds to the upper arm; the third upper limb portion8fcorresponds to the fore-arm and the hand; and a connection portion between the second upper limb portion8uand the third upper limb portion8fcorresponds to the elbow joint. Bending of the elbow is performed by an actuator22provided at the connection portion therebetween.

The first upper limb portion8scorresponds to the shoulder, and an actuator group23disposed at a connection portion between the first upper limb portion8sand the chest4ucan change the roll angle and the pitch angle of the first upper limb portion8s. Meanwhile, an actuator24disposed at a connection portion between the first upper limb portion8sand the second upper limb portion8uimplements a movement equivalent to a twist of the arm.

Each of the left and right lower limbs10includes a thigh10u, a lower thigh10d, and a foot10f. The lower limb10that is a movable leg is connected at the thigh10uthereof under the abdomen4d, and an angle of the lower limb10can be changed around the three axes for rolling, pitching, and yawing by an actuator group25provided at a connection portion corresponding to a hip joint. The lower thigh10dis connected under the thigh10u. A connection portion between the thigh10uand the lower thigh10dcorresponds to a knee joint, and bending of a knee is performed by an actuator26provided at the connection portion.

The foot10fis connected under the lower thigh10dand is positioned at a lower end of the movable leg. A connection portion between the foot10fand the lower thigh10dcorresponds to the foot (ankle) joint, and the roll angle and the pitch angle of the foot10fare changed by an actuator group27provided at the connection portion.

FIG.2is a schematic view depicting a general configuration of a control system for the humanoid robot2. A control unit30includes a processor and a storage device. The processor executes a program stored in the storage device and performs, for example, a process for a signal inputted from sensors31mounted on the humanoid robot2and generates a control signal for actuators32.

It is to be noted that, on the humanoid robot2, the actuators20to27are disposed as the actuators32at the individual joints. Further, the humanoid robot2may have various kinds of sensors31. For example, in a case where the actuator32is configured from a servomotor, also outputs of detectors for the angle, speed, and so forth provided in the servomotor are inputted as signals of the sensors31to the control unit30. Further, especially on the foot10f, a strain sensor for detecting stress generated in a strain generating member in response to the floor reaction force is provided as a sensor relating to the present invention. The control unit30detects a state of the humanoid robot2and motions of the components on the basis of the outputs of the sensors31and controls the various motions including walking. Especially, in control of the walking motion, detection of the center of gravity of the humanoid robot2is required, and to this end, detection of the floor reaction force by the sensors provided on the feet10fis significant.

The control unit30includes, for example, a CPU (Central Processing Unit)33as a processor and further includes a RAM (Random Access Memory)34and a ROM (Read Only Memory)35as storage devices. The control unit30may further include an A/D (Analog-to-Digital) converter36that converts an analog signal outputted from each of the sensors31into a digital signal. The components of the control unit30such as the CPU33, the RAM34, the ROM35, and the A/D converter36are connected to each other, for example, through a bus37, and also the actuators32may be configured so as to be connected to the bus37.

The control unit30is configured using, for example, a microcomputer or the like and is incorporated in the humanoid robot2. Alternatively, the control unit30can be configured as a separate member from the humanoid robot2and connected to the humanoid robot2by a cable or the like.

FIG.3is a schematic exploded perspective view of the foot10f. In the following description, it is assumed that the XYZ coordinate system is a rectangular coordinate system for the right hand system, and the Z axis is a vertical axis; the X axis is a horizontal axis in the leftward and rightward direction; and the Y axis is a horizontal axis in the forward and rearward direction. Further, the positive direction of the Z axis is the upward direction; the positive direction of the X axis is the direction from the right to the left of the humanoid robot2; and the positive direction of the Y axis is the direction from the front to the rear. It is to be noted that, in the present embodiment, the general shape of the foot10fis a plate shape whose thicknesswise direction is the Z direction, and the planar shape of the foot10fis a rectangular having short sides extending along the X direction and long sides extending along the Y direction.

Each of the left and right feet10fhas an instep member that is connected to the lower thigh10dand receives the load of the humanoid robot2, and a sole member that is disposed under the instep member and contacts with the walking surface. The instep member and the sole member are not limited to those configured from a single material but may be configured individually from a plurality of parts or materials.

FIG.3depicts the foot10fin a form in which it is disintegrated into an upper side part including the instep member and a lower side part including the sole member. The upper side part includes an upper frame44having a planar shape of a substantially rectangular shape corresponding to the foot10f. The upper frame44basically corresponds to the instep member. The upper frame44is formed from a material and a structure having high rigidity.

On the other hand, the lower side part includes a lower frame48having a planar shape of a substantially rectangular shape corresponding to the foot10fand strain generating members50and strain sensors52disposed on an upper face of the lower frame48. The lower frame48of the lower side part basically corresponds to the sole member. The lower frame48is formed from a material and a structure having high rigidity. Incidentally, as described hereinabove, the planar shape of the upper frame44and the lower frame48is a substantially rectangular shape corresponding to the foot10f, and the shapes and the sizes of them may be made substantially same as each other. The strain generating members50can be disposed at a plurality of positions in top plan view.

The structure of the foot10fis described in more detail.FIG.4is a schematic side elevational view of the foot10fas viewed in the negative direction of the X axis (namely, as viewed from this side inFIG.3).

A projection as a strain generating member pressing portion64is provided on an edge of the two long sides extending along the Y-axis direction of a lower face of the upper frame44. For example, the strain generating member pressing portion64is disposed at a middle portion of the long sides.

The strain generating members50are attached to the lower frame48that is the sole member and have a function of causing bending deformation according to a change in distance or mutual inclination between the upper frame44and the lower frame48to generate strain according to floor reaction force. In particular, each of the strain generating members50is configured from an elastic body of high rigidity elongated in the Y axis direction, and the strain generating members50are disposed so as to be opposed to the strain generating member pressing portions64of the upper frame44on the two long sides extending along the Y-axis direction of the lower frame48. A projection serving as a support base (strain generating member supporting base70) for the strain generating member50is provided at each of angular portions that form four corners of an upper face of the lower frame48, and the two strain generating member supporting bases70lined up on one long side of the lower frame48support the opposite ends of the strain generating member50disposed on the long side as depicted inFIG.4. Consequently, the strain generating member50is supported such that a middle portion thereof in the Y axis direction is spaced away upwardly from the lower frame48. On the other hand, to the middle portion of the strain generating member50, the strain generating member pressing portion64of the upper frame44is connected. In short, each of the strain generating members50extends in the horizontal direction and is connected at different positions from each other to the upper frame44and the lower frame48such that the upper frame44and the lower frame48apply respective forces to the strain generating members50. Especially, the strain generating member pressing portion64presses the strain generating member50from above with a force according to the load received from the lower thigh10d, and the strain generating member supporting bases70support the strain generating member50from below with a force according to the floor reaction force. Thus, the strain generating member50is acted upon and deformed by forces in the opposite directions at the opposite end portions and the middle portion thereof.

The strain sensors52are installed at a plurality of positions different from each other on the strain generating member50. In particular, each of the strain generating members50extends one-dimensionally in the Y-axis direction (forward and rearward direction), and has connection positions to the lower frame48at a front end portion and a rear end portion thereof and has a connection position to the upper frame44at a middle portion thereof. The strain sensors52are disposed individually between the connection position to the lower frame48of the strain generating member supporting base70at a front end portion of the strain generating member50and the connection position to the upper frame44of the strain generating member pressing portion64at the middle portion and between the connection position to the lower frame48of the strain generating member supporting base70at a rear end portion of the strain generating member50and the connection position to the upper frame44of the strain generating member pressing portion64at the middle portion. In the present embodiment, this structure of the strain generating member50is configured such that the opposite front and rear sides thereof are symmetrical with respect to the strain generating member pressing portion64. For example, the distances from the strain generating member pressing portion64to the strain generating member supporting base70on the front side and the strain generating member supporting base70on the rear side are same as each other, and the distances from the strain generating member pressing portion64to the strain sensor52on the front side and the strain sensor52on the rear side are same as each other.

As has been described above, the strain generating members50are individually disposed on the two long sides extending along the Y-axis direction of the lower frame48, and two strain sensors52are installed on each of the strain generating members50. In short, the strain sensors52are disposed at totaling four positions including rather forward positions and rather rear positions of the left side strain generating member50and the right side strain generating member50as viewed from the middle of the foot10fon an XY plane.

The strain generating members50also have a function as an elastic supporting member that elastically supports the upper frame44, which is the instep member, against the load of the humanoid robot2. In particular, each of the strain generating members50configures a leaf spring. The strain generating member50is deflected downwardly if the strain generating member pressing portion64is pressed against the strain generating member50in response to the load acting upon the upper frame44thereby to exert upward elastic force to the strain generating member pressing portion64.

The load received by the upper frame44changes according to the posture or the motion state of the humanoid robot2, and the strain generating members50elastically support the upper frame44as described hereinabove against the load that is within a supposed range of the change. The rigidity of the strain generating members50can be set low within such a limit that the condition that, for example, even if preliminarily supposed maximum load is applied to any of the strain generating members50, it does not interfere with the lower frame48at the position of the strain generating member pressing portion64is satisfied. In particular, although a condition or a limit can be set, the strain generating member50can be configured so as to be easily deformable, and the strain caused by the floor reaction force or the load becomes great. Therefore, even if the strain sensors52have comparatively low sensitivity, they can detect stress by the floor reaction force or load with a high degree of accuracy.

Here, the rigidity becomes higher when a material having a higher elastic modulus such as a Young's modulus or a modulus of rigidity is used. Further, when the material is same, the rigidity becomes higher if the thickness is increased or a cross section having a higher cross-sectional performance such as an H-shaped cross section or a tubular cross section is used. Also in regard to the rigidity, several types are available corresponding to types of deformation such as bending deformation, axial deformation, shear deformation, and torsional deformation. In the present embodiment, the strain generating members50are leaf springs, and basically the rigidity of them can be defined by bending rigidity. In particular, the bending rigidity k is given, using a Young's modulus E, a moment I of inertia of area, and a distance L between the point of action and the supporting point of force, by k=EI/L. For example, the Young's modulus of each of pure ion, stainless steel, and brass becomes lower in this order. For example, by selection of a material or design of the cross sectional shape from the point of view of the Young's modulus E, the strain generating members50can be formed so as to have rigidity that satisfies the condition described hereinabove. For example, the strain generating members50can be set to minimum rigidity that satisfies the condition described above for the supposed maximum load.

FIGS.5and6depict examples of a case in which the lower frame48receives floor reaction force and are schematic side elevational views similar toFIG.4.FIG.5depicts a case in which the upper frame44is displaced downwardly while keeping a parallel state to the lower frame48. If the upper frame44receives load from the lower thigh10d, then it is displaced downwardly, and the strain generating member50is pushed down and deformed at a middle portion thereof by the strain generating member50. Here, if it is assumed that, for example, the strain generating member50and the strain sensors52are formed symmetrically in the forward and rearward direction with respect to the strain generating member pressing portion64, then in a case where the upper frame44is displaced in a vertical direction while keeping a horizontal state as depicted inFIG.5, also the deformation of the strain generating member50is basically symmetrical at the front and the rear of it, and also the stresses received by the front and rear strain sensors52are same as each other. For example, if it is assumed that the strain sensor52on the front side (left side inFIG.5) with respect to the strain generating member pressing portion64receives compressive stress, then also the strain sensor52on the rear side (right side inFIG.5) receives compressive stress similarly. Basically, the stress increases or decreases together with the vertical displacement amount of the upper frame44, and the vertical displacement amount can be obtained from the magnitude of strain detected by the front and rear strain sensors52.

FIG.6depicts a case in which the upper frame44is inclined to the front side. Here, it is assumed that the distance between the upper frame44and the lower frame48does not vary at the center in the Y direction, namely, the upper frame44is not displaced on the whole in the vertical direction. In this case, a forward end portion of the strain generating member pressing portion64presses down the strain generating member50while a rearward end portion pulls up the strain generating member50. As a result, the deformation of the strain generating member50between the front and the rear becomes basically asymmetrical, and also the stress received by the strain sensor52becomes asymmetrical. For example, the strain sensor52on the front side (left side inFIG.5) with respect to the strain generating member pressing portion64receives compressive stress while the strain sensor52on the rear (right side inFIG.5) receives tensile stress. Basically, the absolute value of the stress increases or decreases together with an inclination amount of the upper frame44, and the inclination amount of the upper frame44in the forward and rearward direction (around the X axis) can be obtained from the difference between strains detected by the front and rear strain sensors52.

On the other hand, if the two long sides extending along the Y axis direction of the lower frame48are represented as left side long side and right side long side, then the inclination amount in the leftward and rightward direction (around the Y axis) of the upper frame44can be obtained from the difference between the strain detected by the strain sensor52on the left side long side and the strain detected by the strain sensor52on the right side long side. For example, in a case where the upper frame44is inclined such that the left side lowers and the right side rises without being displaced in the vertical direction on the whole, on the left side long side, the strain generating member pressing portion64pushes down the strain generating member50, and the strain sensor52on the long side detects a downward vertical displacement of the upper frame44. Meanwhile, on the right side long side, the strain generating member pressing portion64pulls up the strain generating member50, and the strain sensor52on the long side detects an upward vertical displacement of the upper frame44. In short, in regard to the inclination in the leftward and rightward direction of the upper frame44, basically the deformation of the strain generating members50on the long sides on the opposite left and right sides becomes asymmetrical, and also the stress received by the strain sensor52becomes asymmetrical between the two long sides. Basically, the difference between the stresses increases or decreases together with the inclination amount of the upper frame44, and the inclination amount in the leftward and rightward direction of the upper frame44can be obtained from the difference between the strains detected by the left and right strain sensors52as described hereinabove.

As described hereinabove, the strain sensors52disposed at the four locations of the foot10fform part of the various sensors31, and output signals are inputted to the control unit30therefrom. For example, the control unit30uses the output signals of the strain sensors52to calculate the floor reaction force at each of the right and left feet and the center of gravity of the humanoid robot2, and further controls the walking movement using results of the calculation. In particular, the control unit30calculates, on the basis of measurement values of the stress obtained by the strain sensors52at a plurality of positions in the XY plane of one foot10f, a floor reaction force vector acting on the foot10f(composite vector of the floor reaction force over the overall sole) and the point of action of the floor reaction force vector. In the present embodiment, the strain sensors52are disposed at four locations such as front, rear, left, and right in the XY plane and can calculate, basically using the outputs of the strain sensors52, a displacement amount in the vertical direction of the upper frame44and inclination amounts in the forward and rearward direction and the leftward and rightward direction of the upper frame44as described hereinabove. Furthermore, two-dimensional coordinates in the XY plane of the point of action of the floor reaction force on the foot10fcan be obtained, and the floor reaction force can be obtained as a three-dimensional vector in the XYZ space. It is to be noted that the point of action and the vector of the floor reaction force can be calculated from measurement values of the strain sensors52basically at three or more locations in the XY plane. Further, the control unit30calculates the ZMP of the humanoid robot2on the basis of the outputs of the strain sensors52.

It is to be noted that, although the strain sensors52in the present embodiment are installed on the upper face of the strain generating member50, they may otherwise be installed on the lower face. Further, although the strain generating members in the present embodiment are disposed on a pair of sides extending along the forward and rearward direction of the foot10fof a substantially rectangular shape, they may otherwise be disposed on a pair of sides extending along the leftward and rightward direction or may be disposed on all of the four sides. Here, if the case in which the strain generating members50are disposed on the long sides of the rectangular shape and the case in which the strain generating members50are disposed on the short sides of the rectangular shape are compared with each other, then if the Young's modulus E and the moment I of inertia of area are in common to both cases, then in the former case, the distance L between the point of action and the supporting point of a force becomes greater and the bending rigidity k becomes smaller, and therefore, the strain generating members50are easier to be deformed.