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运动控制中的Jerk
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Jerk是加速度对时间的导数，单位是m/s3 ，即米/秒的3次方。Jerk可以看做是加速度的变化率。 在运动控制中，通过调整Jerk可以使得运动更加平滑，其具体描述如下，摘自维基百科， In motion control, the design focus is on straight, linear motion, with the need to move a system from one steady position to another (point-to-point motion). The design concern from a jerk perspective is vertical jerk; the jerk from tangential acceleration is effectively zero since linear motion is non-rotational. Motion control applications include passenger elevators and machining tools. Limiting vertical jerk is considered essential for elevator riding convenience.[6] ISO 18738[7] specifies measurement methods for elevator ride quality with respect to jerk, acceleration, vibration, and noise; however, the standard does specify levels for acceptable or unacceptable ride quality. It is reported[8] that most passengers rate a vertical jerk of 2 m/s3 as acceptable and 6 m/s3 as intolerable. For hospitals, 0.7 m/s3 is the recommended limit. A primary design goal for motion control is to minimize the transition time without exceeding speed, acceleration, or jerk limits. Consider a third-order motion-control profile with quadratic ramping and deramping phases in velocity (see figure).
This motion profile consists of the following seven segments: Acceleration build up — positive jerk limit; linear increase in acceleration to the positive acceleration limit; quadratic increase in velocityUpper acceleration limit — zero jerk; linear increase in velocityAcceleration ramp down — negative jerk limit; linear decrease in acceleration; (negative) quadratic increase in velocity, approaching the desired velocity limitVelocity limit — zero jerk; zero accelerationDeceleration build up — negative jerk limit; linear decrease in acceleration to the negative acceleration limit; (negative) quadratic decrease in velocityLower deceleration limit — zero jerk; linear decrease in velocityDeceleration ramp down — positive jerk limit; linear increase in acceleration to zero; quadratic decrease in speed; approaching the desired position at zero speed and zero accelerationSegment four’s time period (constant velocity) varies with distance between the two positions. If this distance is so small that omitting segment four would not suffice, then segments two and six (constant acceleration) could be equally reduced, and the constant velocity limit would not be reached. If this modification does not sufficiently reduce the crossed distance, then segments one, three, five, and seven could be shortened by an equal amount, and the constant acceleration limits would not be reached. Other motion profile strategies are used, such as minimizing the square of jerk for a given transition time[9] and, as discussed above, sinusoidal-shaped acceleration profiles. Motion profiles are tailored for specific applications including machines, people movers, chain hoists, automobiles, and robotics. |
上图中，相邻2者，下面的是上面的对时间求导的结果，可以看出Jerk后面还有一些。
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