我使用Pymunk来模拟安装在细长腿上的枢轴上的盒子的物理特性，该腿附着在地面上。将盒子连接到腿部的枢轴是PivotJoint和SimpleMotor的组合，模拟原始伺服，用户可以打开和关闭以将盒子的质心移到腿上。以下是我实现此模型的Pymunk + Pygame代码：
from __future__ import print_function
import sys
from math import pi
import pygame
from pygame.locals import USEREVENT, QUIT, KEYDOWN, KEYUP, K_s, K_r, K_q, K_ESCAPE, K_UP, K_DOWN
from pygame.color import THECOLORS
import pymunk
from pymunk import Vec2d
import pymunk.pygame_util
LEG_GROUP = 1
class Simulator(object):
def __init__(self):
self.display_flags = 0
self.display_size = (600, 600)
self.space = pymunk.Space()
self.space.gravity = (0.0, -1900.0)
self.space.damping = 0.999 # to prevent it from blowing up.
# Pymunk physics coordinates start from the lower right-hand corner of the screen.
self.ground_y = 100
ground = pymunk.Segment(self.space.static_body, (5, self.ground_y), (595, self.ground_y), 1.0)
ground.friction = 1.0
self.space.add(ground)
self.screen = None
self.draw_options = None
def reset_bodies(self):
for body in self.space.bodies:
if not hasattr(body, 'start_position'):
continue
body.position = Vec2d(body.start_position)
body.force = 0, 0
body.torque = 0
body.velocity = 0, 0
body.angular_velocity = 0
body.angle = body.start_angle
def draw(self):
### Clear the screen
self.screen.fill(THECOLORS["white"])
### Draw space
self.space.debug_draw(self.draw_options)
### All done, lets flip the display
pygame.display.flip()
def main(self):
pygame.init()
self.screen = pygame.display.set_mode(self.display_size, self.display_flags)
width, height = self.screen.get_size()
self.draw_options = pymunk.pygame_util.DrawOptions(self.screen)
def to_pygame(p):
"""Small hack to convert pymunk to pygame coordinates"""
return int(p.x), int(-p.y+height)
def from_pygame(p):
return to_pygame(p)
clock = pygame.time.Clock()
running = True
font = pygame.font.Font(None, 16)
# Create the torso box.
box_width = 50
box_height = 100
leg_length = 100
leg_thickness = 2
mass = 200
points = [(-box_width/2, -box_height/2), (-box_width/2, box_height/2), (box_width/2, box_height/2), (box_width/2, -box_height/2)]
moment = pymunk.moment_for_poly(mass, points)
body1 = pymunk.Body(mass, moment)
body1.position = (self.display_size[0]/2, self.ground_y+box_height/2+leg_length)
body1.start_position = Vec2d(body1.position)
body1.start_angle = body1.angle
shape1 = pymunk.Poly(body1, points)
shape1.group = LEG_GROUP
shape1.friction = 0.8
shape1.elasticity = 0.0
self.space.add(body1, shape1)
# Create bar 2 extending from the right to the origin.
mass = 10
points = [
(leg_thickness/2, -leg_length/2),
(-leg_thickness/2, -leg_length/2),
(-leg_thickness/2, leg_length/2-leg_thickness),
(leg_thickness/2, leg_length/2-leg_thickness/2)
]
moment = pymunk.moment_for_poly(mass, points)
body2 = pymunk.Body(mass, moment)
body2.position = (self.display_size[0]/2-box_width/2, self.ground_y+leg_length/2)
body2.start_position = Vec2d(body2.position)
body2.start_angle = body2.angle
shape2 = pymunk.Poly(body2, points)
shape2.group = LEG_GROUP
shape2.friction = 0.8
shape2.elasticity = 0.0
self.space.add(body2, shape2)
# Link bars together at end.
pj = pymunk.PivotJoint(body1, body2, (self.display_size[0]/2-box_width/2, self.ground_y+leg_length-leg_thickness))
self.space.add(pj)
# Attach the foot to the ground in a fixed position.
pj = pymunk.PivotJoint(self.space.static_body, body2, (self.display_size[0]/2-box_width/2, self.ground_y+leg_thickness))
self.space.add(pj)
# Actuate the bars via a motor.
motor_joint = pymunk.SimpleMotor(body1, body2, 0)
self.space.add(motor_joint)
# Add hard stops to leg pivot so the torso can't rotate through leg.
hip_limit_joint = pymunk.RotaryLimitJoint(body1, body2, -pi/4., pi/4.) # -45deg:+45deg
self.space.add(hip_limit_joint)
pygame.time.set_timer(USEREVENT+1, 70000) # apply force
pygame.time.set_timer(USEREVENT+2, 120000) # reset
pygame.event.post(pygame.event.Event(USEREVENT+1))
pygame.mouse.set_visible(False)
simulate = False
while running:
# print('angles:', body1.angle, body2.angle)
servo_angle = (body1.angle - body2.angle) * 180/pi # 0 degrees means leg is angled straight down
servo_cw_enabled = servo_angle > -45
servo_ccw_enabled = servo_angle < 45
for event in pygame.event.get():
if event.type == QUIT or (event.type == KEYDOWN and event.key in (K_q, K_ESCAPE)):
#running = False
sys.exit(0)
elif event.type == KEYDOWN and event.key == K_s:
# Start/stop simulation.
simulate = not simulate
elif event.type == KEYDOWN and event.key == K_r:
# Reset.
# simulate = False
self.reset_bodies()
elif event.type == KEYDOWN and event.key == K_UP:
if servo_ccw_enabled:
motor_joint.rate = 5
else:
motor_joint.rate = 0
elif event.type == KEYDOWN and event.key == K_DOWN:
if servo_cw_enabled:
motor_joint.rate = -5
else:
motor_joint.rate = 0
elif event.type == KEYUP:
motor_joint.rate = 0
self.draw()
### Update physics
fps = 50
iterations = 25
dt = 1.0/float(fps)/float(iterations)
if simulate:
for x in range(iterations): # 10 iterations to get a more stable simulation
self.space.step(dt)
pygame.display.flip()
clock.tick(fps)
if __name__ == '__main__':
sim = Simulator()
sim.main()
按下＆＃34; s＆＃34;开始模拟。然后使用上/下键围绕腿旋转盒子。它主要表现如预期......直到它接触地面，然后它开始反弹＆＃34;猛烈。 See this screen capture举个例子。
如何阻止这种情况？我通过赋予它很多质量来使盒子变得非常沉重，并且我已经将所有东西的弹性设置为0.如果每次更新使用少于10次迭代，文档会提到可能有弹性或松软的东西，但我正在使用25.我还缺少什么呢？
答案 0 :(得分：1)
尝试设置电机接头的max_force。没有它，电机接头可以使用无限大功率。
例如：motor_joint.max_force = 100000000
另请注意，两个形状上的组设置错误。 shape2.group = LEG_GROUP没有做任何事情。在以前的版本（＆lt; 5.0）中，组的工作方式如此，但现在您应该使用ShapeFilter：shape1.filter = pymunk.ShapeFilter(group=LEG_GROUP)