robot

Abstract

To provide a robot which corrects a moment vector around a center of gravity to adjust a floor reaction moment.SOLUTION: A leg type mobile robot comprises: a calculation part in which a floor reaction moment around a vertical axis is calculated based on a center of gravity of a robot, a ZMP track and a moment track around the center of gravity, and when the floor reaction moment around the vertical axis exceeds a friction limit, a correction amount of the moment vector around the center of gravity is calculated; and a controller which controls the robot based on the correction amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to robots. [Background technology]

[0002] Patent Document 1 describes setting an allowable range for a limiting quantity which is the vertical component of the ground reaction force moment, the component of the ground reaction force moment in the direction normal to the floor surface, or the vertical component of the rate of change of angular momentum of the robot, or the component of the rate of change of angular momentum in the direction normal to the floor surface. It also describes inputting at least a provisional instantaneous value of the target motion into a dynamics model to obtain the instantaneous value of the model limiting quantity as the output of the dynamics model. Finally, it describes correcting the provisional instantaneous value of the target motion so that at least the instantaneous value of the model limiting quantity falls within the allowable range to determine the instantaneous value of the target motion. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2005 / 000535 [Overview of the project] [Problems that the invention aims to solve]

[0004] Patent Document 1 describes modifying the arm swing acceleration so that it falls within the upper and lower limits of the ground reaction force moment around the vertical axis. However, there is a risk that the ground reaction force moment cannot be adjusted using only the force generated by the arm swing. Therefore, the object of this disclosure is to provide a robot that adjusts the ground reaction force moment by modifying the moment vector around the center of gravity. [Means for solving the problem]

[0005] The robot in this disclosure is It is a robot that moves on its legs. A calculation unit calculates the ground reaction force moment around the vertical axis from the robot's center of gravity and ZMP (Zero Moment Point) trajectory and the moment trajectory around the center of gravity, and determines the correction amount for the moment vector around the center of gravity if the ground reaction force moment around the vertical axis exceeds the friction limit. A control unit that controls the robot based on the aforementioned correction amount, A robot equipped with [the following features].

[0006] Based on the above features, we can provide a robot that adjusts the ground reaction force moment by correcting the moment vector around the center of gravity.

[0007] The robot in this disclosure is The calculation unit is characterized by determining the correction amount such that the norm is minimized.

[0008] The reason for the above characteristics is that it is preferable to minimize the amount of correction.

[0009] The robot in this disclosure is The control unit is characterized by correcting the acceleration and deceleration of the center of gravity trajectory according to the amount of correction.

[0010] Due to the above characteristics, it is possible to modify the moment vector around the center of gravity without changing the ZMP by changing the acceleration of the center of gravity.

[0011] The robot in this disclosure is The calculation unit determines whether the amount of correction for the moment around the vertical axis center of gravity exceeds the limit value when the floor reaction force moment around the vertical axis exceeds the friction limit. The control unit modifies only the moment about the vertical axis center of gravity if the amount of correction of the moment about the vertical axis center of gravity does not exceed the limit. The method is characterized by correcting the moment vector about the center of gravity if the amount of correction to the moment about the center of gravity of the vertical axis exceeds a limit.

[0012] The reason for the above characteristics is that if the moment component around the center of gravity around the horizontal axis is corrected, the ZMP will deviate from the expected value. Therefore, if it is possible to correct the issue by correcting only the moment around the vertical center of gravity, it is preferable to correct only the moment around the vertical center of gravity.

[0013] The robot in this disclosure is The calculation unit calculates the moment around the vertical axis center of gravity based on the range of motion and velocity range of arm swing and torso twist, The control unit is characterized by compensating the floor reaction force moment around the vertical axis based on the calculated moment around the vertical axis center of gravity.

[0014] Based on the above characteristics, it is possible to determine the amount of correction for the moment around the vertical center of gravity from the vertical axial moment that can be generated by arm swing and torso twisting. [Effects of the Invention]

[0015] This disclosure provides a robot that adjusts the ground reaction moment by correcting the moment vector around the center of gravity. [Brief explanation of the drawing]

[0016] [Figure 1] This is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 1. [Figure 2] This is a block diagram for determining the correction amount of the moment vector around the center of gravity according to Embodiment 2. [Figure 3] This is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 3. [Figure 4] This figure shows the center of gravity and positional relationship of the robot arm according to Embodiment 4. [Figure 5] This is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 4. [Figure 6] This is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 5. [Figure 7]This is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 6. [Figure 8] This is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 7. [Modes for carrying out the invention]

[0017] Embodiment 1 Embodiments of the present invention will be described below with reference to the drawings. However, the invention claimed is not limited to the following embodiments. Furthermore, not all of the configurations described in the embodiments are necessarily essential for solving the problem. For clarity of explanation, the following descriptions and drawings have been omitted and simplified as appropriate. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations have been omitted where necessary.

[0018] (Explanation of related technologies) A robot that moves using associated legs comprises a calculation unit that calculates the robot's posture and a control unit that controls the robot's posture. The robot's calculation unit and control unit may be built into the robot itself, or the robot may be operated remotely. The processing performed by the calculation unit and control unit is carried out using a processor (e.g., a CPU (Central Processing Unit)) that executes a program to perform the processing, and memory that stores the program.

[0019] The equation of motion for the center of gravity of a legged mobile robot is expressed as the equilibrium equation for translational forces,

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[0020] The Zero Moment Point (ZMP) is the point where the ground reaction moment around the horizontal axis becomes zero in relation to the equation of motion of the center of mass. The equation for moment equilibrium at the ZMP is:

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[0021] Here, the ZMP equation is based on the premise that equation (3) holds, but the floor reaction moment n around the vertical axis of the ZMP zIt depends on the friction acting between the floor surface and the sole of the foot. Therefore, Equation (3) does not always hold. Thus, the floor reaction moment around the vertical axis can be calculated from the ZMP trajectory and the moment trajectory around the center of gravity. When Equation (3) does not hold, that is, when n z is insufficient, the sole of the foot slips around the Yaw axis, causing problems such as instability of grounding and falling.

[0022] Therefore, in order to make Equation (3) hold conventionally, Equations (1) and (2) are not changed, and the moment L z · around the center of gravity of the vertical axis is corrected to cope with it. For example, the limit value of n z due to the friction limit is set as n z limit , and when n z is greater than the limit value, the moment L z · around the center of gravity of the vertical axis is corrected as ΔL z · = n z limit · as shown. By doing so, z n

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[0023]

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[0024] As can be seen from the above, when attempting to achieve high-speed running or dynamic movements, the swing of the free leg, etc., creates a moment L around the vertical axis of the center of gravity. z • will take on a large value. Therefore, assuming that friction does not change, the correction amount ΔL z • A larger value is needed. However, the moment around the vertical axis center of gravity that can be generated by additional arm swings or torso twists is limited in terms of range of motion and joint velocity. For this reason, for example, as running speed increases, n z The amount of correction ΔL for exceeding the friction limit z The problem arises that corrections by [method name] cannot fully compensate for the issue.

[0025] (Explanation of the correction of the moment vector around the center of gravity according to Embodiment 1) Figure 1 is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 1. The correction of the moment vector around the center of gravity according to Embodiment 1 will be explained with reference to Figure 1.

[0026] This disclosure proposes addressing a deficiency in the ground reaction moment around the vertical axis not only by correcting the moment around the vertical axis center of gravity, but also by correcting the moments around the center of gravity of all three axes, i.e., the moment vectors around the center of gravity. Furthermore, since it is desirable that the amount of correction be as small as possible, it is preferable that the amount of correction of the moment vectors around the center of gravity is determined so that its norm is minimized.

[0027] First, we define L· as the moment vector around the center of gravity and p as the vector representing the position of the center of gravity as seen from ZMP, as follows.

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[0028] Therefore, the correction amount ΔL· is corrected to n z to n z limit When restricted to within, equation (5) becomes,

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[0029] As shown in Figure 1, the target trajectory is obtained by equation (4) (step S101). Equation (5) gives the ground reaction moment n around the vertical axis. z This is calculated (step S102). Next, n z It is determined whether or not it is within the friction limit (step S103). z If it is within the friction limit (if Yes in step S103), the whole body posture is determined (step S106). z If the friction limit is not met (case No. in step S103), the correction amount for the moment vector around the center of gravity is calculated using equation (12) (step S104). After calculating the correction amount (step S105), the whole-body posture is determined (step S106). In this way, a robot can be provided that adjusts the ground reaction force moment by correcting the moment vector around the center of gravity.

[0030] (Explanation of the correction of the moment vector around the center of gravity according to Embodiment 2) Figure 2 is a block diagram for determining the correction amount of the moment vector around the center of gravity in Embodiment 2. The correction of the moment vector around the center of gravity in Embodiment 2 will be explained with reference to Figure 2.

[0031] In Embodiment 1, the moment vector L· around the center of gravity was modified without changing the center of gravity trajectory, resulting in a change in ZMP. However, it is also possible to modify the moment vector L· around the center of gravity without changing ZMP by changing the center of gravity acceleration.

[0032] In that case, from equations (1) and (2), the change in the center of gravity acceleration is:

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[0033] If the center of mass trajectory is changed, the center of mass trajectory at subsequent time points will also be affected and diverge. Therefore, in the method of this embodiment, it is essential to regenerate the trajectory in accordance with the changed center of mass trajectory, in combination with online trajectory generation.

[0034] Figure 2 shows a block diagram combining online trajectory generation and the calculation of the correction amount for the moment vector around the center of mass. By passing the change in the center of mass due to the correction of the center of mass acceleration as the current value to online trajectory generation, the center of mass trajectory is regenerated from the center of mass position and velocity after acceleration and deceleration, making it possible to continue the motion stably. The moment vector around the center of mass is corrected using equation (16). The center of mass acceleration is corrected using equations (13) and (14).

[0035] Furthermore, by using this embodiment simultaneously with Embodiment 1 and distributing equations (6), (7) and (13), (14) in a fixed proportion, it is also possible to configure it in a way that reduces the variation amount of ZMP, equations (6) and (7). In that case, T p →kT p Then, using equation (12), the correction amount ΔL· is calculated, and the acceleration correction amounts in equations (13) and (14) are multiplied by (1-k) to update the center of mass trajectory.

[0036] This method allows for the modification of the moment vector around the center of gravity without changing the ZMP by altering the acceleration of the center of gravity.

[0037] (Explanation of the correction of the moment vector around the center of gravity according to Embodiment 3) Figure 3 is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 3. The correction of the moment vector around the center of gravity according to Embodiment 3 will be explained with reference to Figure 3.

[0038] In embodiments 1 and 2, when the ground reaction force moment around the vertical axis exceeded the friction limit, the moment vector L· around the center of gravity was corrected. However, if the moment component around the center of gravity around the horizontal axis is corrected, the ZMP will deviate from the assumption. Moment L around the center of gravity on the vertical axis z If the issue can be resolved by simply correcting the vertical axis centroid, then the moment L z It is preferable to only make corrections to the above.

[0039] Therefore, in Embodiment 3, before correcting the moment vector about the center of gravity in Embodiment 1, the amount of correction for the moment about the vertical axis center of gravity is calculated, and that amount of correction is the upper and lower limit ΔL z lower ·, ΔL z upper The system checks whether the value exceeds a certain threshold and, based on the result, modifies whether only the moment around the vertical center of gravity is corrected, or whether the moment vector around the center of gravity is also corrected.

[0040] The correction amount ΔLz· is, as mentioned above, ΔL z ·=n z -n z limit ...(17) Let ΔL z lower ·, ΔL z upper For this, we will treat it as a predetermined fixed parameter.

[0041] As shown in Figure 3, steps S301, S302, and S303 are the same as steps S101, S102, and S103 of Embodiment 1, so their explanation is omitted. z If it is not within the friction limit (No in step S303), the correction amount for the moment around the vertical axis centroid is calculated using equation (17) (step S304). Next, the correction amount ΔL z Determine whether it is within the limit (step S305). Correction amount ΔL z If it is within the limit (if Yes in step S305), the moment L about the vertical axis centroid z Correct the posture (step S306). Then determine the overall posture (step S309).

[0042] Correction amount ΔL z If the value is not within the limit (case No in step S305), calculate the correction amount for the moment vector around the center of gravity (step S307). Next, correct the moment vector L· around the center of gravity (step S308). Finally, determine the whole body posture (step S309).

[0043] If this method corrects the moment component around the center of gravity around the horizontal axis, the ZMP will deviate from the expected value. Therefore, if it is possible to correct the issue by only correcting the moment around the vertical center of gravity, then only the moment around the vertical center of gravity can be corrected.

[0044] (Explanation of the correction of the moment vector around the center of gravity according to Embodiment 4) Figure 4 shows the center of gravity and positional relationship of the robot arm according to Embodiment 4. Figure 5 is a flowchart for determining the amount of correction of the moment vector around the center of gravity according to Embodiment 4. The correction of the moment vector around the center of gravity according to Embodiment 4 will be explained with reference to Figures 4 and 5.

[0045] In Embodiment 3, the upper and lower limits ΔL of the correction amount for the moment around the vertical axis centroid z lower ·, ΔL z upper Although the parameters are fixed, these parameters should ideally be determined from the vertical axial moment that can be generated by arm swing or torso twisting. In Embodiment 4, ΔL is derived from the range of motion or velocity limit, which is the position for a preset arm swing or torso twisting motion. z lower ·, ΔL z upper Add a process to set the following:

[0046] Figure 4 shows a schematic diagram and a top view of the robot. 401 is the center of gravity of the entire left arm. larm This indicates that m rarm This indicates the center of gravity of the entire right arm. larm , x rarm d is the position of the arm's center of gravity in the direction of movement, larm d rarm This represents the distance in the y-direction from the overall center of gravity to the center of gravity of each arm.

[0047] At this time, the moment ΔL around the vertical axis center of gravity is generated by the swing of the arm, i.e., by the acceleration correction of the arm's center of gravity. z ·teeth,

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[0048] The constraint on the position of each arm's center of gravity is x larm lower , x rarm upper Let the speed limit be x larm lower ·, x rarmupper · (where · represents the first derivative), when using a suitable time constant τ, the acceleration correction amount Δx of the arm center of gravity larm ··, Δx rarm ·· (where ·· represents the second derivative) ranges from

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[0049] ] ]By comparing the ranges of the acceleration correction amounts due to position - velocity limits in Equation (19) and Equation (20), the upper and lower limits of the acceleration correction amounts for each arm are ] ]

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[0050] As shown in Figure 5, steps S501, S502, and S503 are the same as steps S101, S102, and S103 in Embodiment 1, so their explanation is omitted. z If the value is not within the friction limit (case No. in step S503), the upper and lower limits of the correction amount for the moment around the vertical axis center of gravity are calculated using equations (21) and (22). Next, the correction amount for the moment around the vertical axis center of gravity is calculated using equation (17). Steps S506, S507, S508, S509, and S510 are the same as steps S305, S306, S307, S308, and S309 of Embodiment 3, so their explanation is omitted.

[0051] The above method allows for the determination of the amount of correction to the moment around the vertical axis center of gravity from the vertical axis moment that can be generated by arm swing and torso twisting. In this embodiment, only the correction of the moment around the vertical axis center of gravity due to arm swing is described, but a similar discussion can be held regarding the correction of the moment around the center of gravity due to torso twisting, by considering, for example, the range of motion of the torso yaw axis joint, speed limits, and torque limits.

[0052] (Explanation of the correction of the moment vector around the center of gravity according to Embodiment 5). Figure 6 is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 5. The correction of the moment vector around the center of gravity according to Embodiment 5 will be explained with reference to Figure 6.

[0053] In Embodiment 1, it was stated that the ZMP fluctuates in conjunction with the correction of the moment vector around the center of gravity. In Embodiment 5, a process is added to determine the correction amount ΔL· of the moment vector around the center of gravity while limiting the amount of ZMP fluctuation so that the ZMP does not extend beyond the support region.

[0054] The ZMP fluctuation is expressed as shown in equations (6) and (7), so the range of ZMP in the x and y directions is x zmp lower , x zmp upper , y zmp lower , y zmp upper Given the above, the upper and lower limits of the correction amount for the moment around the horizontal axis centroid are:

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[0055] If we combine equations (23) and (24) into matrices,

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[0056] Furthermore, equation (10) is,

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[0057] Equation (27) is a convex quadratic programming problem and can be solved quickly using various existing methods such as the interior-point method or the active-set method.

[0058] As shown in Figure 6, steps S601, S602, and S603 are the same as steps S101, S102, and S103 of Embodiment 1, so their explanation is omitted. z If the friction limit is not reached (case No in step S603), the upper and lower limits of the ZMP limit are obtained (step S604). Next, the upper and lower limits of the correction amount for the moment vector around the center of mass are calculated using equations (23) and (24) (step S605). Next, the coefficients P, q, V, and w of the optimization problem are calculated using equations (25) and (26) (step S606). Next, the convex quadratic programming problem is solved using equation (27) (step S607). Next, the moment vector around the center of mass is corrected (step S608) and the whole-body posture is determined (step S609).

[0059] Using the method described above, the calculation unit can calculate the upper and lower limits of the horizontal axis component of the correction amount of the moment vector around the center of gravity based on the tolerance range of the ZMP, and determine the correction amount of the moment vector around the center of gravity using convex quadratic programming. Therefore, it is possible to restrict the ZMP and prevent it from going outside the support region.

[0060] (Explanation of the correction of the moment vector around the center of gravity according to Embodiment 6) Figure 7 is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 6. The correction of the moment vector around the center of gravity according to Embodiment 6 will be explained with reference to Figure 7.

[0061] Embodiment 6 combines Embodiments 4 and 5 and is configured to include a determination of correction of the moment around the vertical axis center of gravity before the correction of the moment vector around the center of gravity. As shown in Figure 7, steps S701, S702, and S703 are the same as steps S101, S102, and S103 of Embodiment 1, so their explanation is omitted. Steps S704, S705, S706, and S707 are the same as steps S504, S505, S506, and S507 of Embodiment 4. Steps S708, S709, S710, S711, and S712 are the same as steps S604, S605, S606, S607, and S608 of Embodiment 5.

[0062] As can be seen in Figure 7, within the limits of arm swing restrictions, i.e., within the upper and lower limits of the correction of the moment around the vertical axis center of gravity, when the ground reaction force moment around the vertical axis can be compensated, the moment vector correction around the center of gravity is not performed.

[0063] (Explanation of the correction of the moment vector around the center of gravity according to Embodiment 7) Figure 8 is a flowchart for determining the correction amount of the moment vector around the center of gravity according to Embodiment 7. The correction of the moment vector around the center of gravity according to Embodiment 7 will be explained with reference to Figure 8.

[0064] Embodiment 7 constructs the optimization problem by adding not only the ZMP constraint of Embodiment 6, but also a constraint on the amount of correction of the moment around the vertical axis centroid. Specifically, by adding equations (21) and (22) to equation (23),

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[0065] With this configuration, the calculation unit calculates a limit value for the correction amount of the moment around the vertical axis center of gravity based on the range of motion and velocity of arm swing and torso twist. It then determines the correction amount of the moment vector around the center of gravity using a convex quadratic programming method that uses the upper and lower limits of the horizontal axis component of the correction amount of the moment vector around the center of gravity based on the allowable range of ZMP and the upper and lower limits of the vertical component of the correction amount of the moment vector around the center of gravity. As a result, the smallest correction amount of the moment vector around the center of gravity can be obtained while satisfying constraints such as the constraints and arm swing restrictions. Furthermore, similar to Embodiment 6, if the issue can be addressed by correcting only the moment around the vertical axis center of gravity, the correction of the moment vector around the center of gravity accompanied by ZMP fluctuations is not performed, so the best course of action can be taken depending on the situation.

[0066] As shown in Figure 8, steps S801, S802, and S803 are the same as steps S101, S102, and S103 in Embodiment 1, so their explanation is omitted. Steps S804, S805, S806, and S807 are the same as steps S504, S505, S506, and S507 in Embodiment 4. Steps S808 and S809 are the same as steps S604 and S605 in Embodiment 6.

[0067] Next, using equations (26) and (28), we obtain the coefficient P of the optimization problem. c , q c Calculate V and w (step S810). Next, solve the convex quadratic programming problem using equation (29) (step S811). Next, correct the moment vector around the center of mass (step S812). Finally, determine the whole body posture (step S813).

[0068] Furthermore, although this embodiment is based on Embodiment 1, it is also possible to combine it with the configuration of Embodiment 2, for example, by reflecting the effect of the correction amount ΔL· of the moment vector around the center of gravity not only in the ZMP fluctuation but also in part of the acceleration correction, or by introducing a slack variable into the ZMP constraint of Equation 28 and reflecting only the amount of the constraint violation in the acceleration correction.

[0069] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0070] 401 Center of gravity of the left arm

Claims

1. It is a robot that moves on its legs. A calculation unit calculates the ground reaction force moment around the vertical axis from the robot's center of gravity and ZMP (Zero Moment Point) trajectory and the moment trajectory around the center of gravity, and determines the correction amount for the moment vector around the center of gravity if the ground reaction force moment around the vertical axis exceeds the friction limit. A control unit that controls the robot based on the aforementioned correction amount, Equipped with, The calculation unit determines whether the amount of correction for the moment around the vertical axis center of gravity exceeds the limit value when the floor reaction force moment around the vertical axis exceeds the friction limit. The control unit modifies only the moment about the vertical axis center of gravity if the amount of correction of the moment about the vertical axis center of gravity does not exceed the limit. A robot that modifies the moment vector around the center of gravity if the amount of correction to the moment around the vertical axis center of gravity exceeds a limit.

2. The robot according to claim 1, wherein the calculation unit determines the correction amount of the moment vector about the center of gravity such that the norm of the moment vector about the center of gravity is minimized.

3. The robot according to claim 1, wherein the control unit corrects the acceleration and deceleration of the center of gravity trajectory according to the correction amount of the moment vector about the center of gravity.

4. The calculation unit calculates the moment around the vertical axis center of gravity based on the range of motion and velocity range of arm swing and torso twist, The robot according to claim 1, wherein the control unit compensates the floor reaction force moment around the vertical axis based on the calculated moment around the vertical axis center of gravity.

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