S-200-

 -300,

 -400
 0 15 30 45 60 75 90
 Time (1/60 sec)


 3 800.
 M ^ 600-
 | 400-
 UL 200.
 0-
 -200 ., 1. .. .
 0 15 30 45 60 75 90
 Time (1/60 sec)

 Figure 6.6. Typical response of joint 2 of the orange-picking robot to a step input of 750 D/A
 bits.


 Table 6.3. Steady-state gains, hydraulic damping ratios, and hydraulic natural frequencies as
 determined by analysis of the step test responses.

 averaged averaged
 steady-state averaged hydraulic natural
 gain hydraulic damping frequency
 (deg/sec) ratio (rad/sec (HZ))
 joint (D/A word) nin max rin max
 0 0.039 0.18 0.34 17 (2.8) 33 (5.2)
 1 0.056 0.18 0.32 22 (3.5) 32 (5.1)


 Similarly, step test responses of joint 1 produced information for estimating the

parameters of its transfer function. Once again, the tests were conducted in both directions with

different positions of joint 2 for establishing a range of the parameters which were valid for

the manipulator during operation. Also listed in Table 6.3, the system open-loop gain was

estimated as a constant value of 0.056 (deg/sec)/(D/A word), while the average hydraulic