CHAPTER 7
 PERFORMANCE CRITERIA


 Desired performance criteria for the joint control systems of the orange-picking robot

 are specified in this chapter. Because joint control was based on position, velocity, and vision

 information, performance requirements were defined to give details upon which the control

 systems would be designed and evaluated. In order to determine these requirements, the

 interaction between the robot and its environment was evaluated. Initially, the motions of a

 fruit hanging from the tree were examined. Information acquired from this investigation was

 used to establish vision dynamic criteria for the robot's control. To determine the precision

 with which the end-effector of the robot was required to be positioned, a picking envelope was

 established. This picking envelope defined the volume with respect to the end-effector in

 which a fruit must be located to be picked. In other words, the controllers were required to

 utilize information from the fruit sensors to position the end-effector within reach of the

 targeted fruit. From this definition of fruit motion and the pick envelope, controller

 performance criteria for each joint were determined. These requirements make up the static and

 dynamic performance criteria which were necessary for choosing and designing controllers to

 realize a satisfactory robot response.


 Background

 All control systems are designed to perform a specific task. Performance specifications

are spelled out as requirements of the control system. These criteria include relative stability,

accuracy, and response rate. In most cases, these specifications are given in precise numerical

values. However, in some cases, the criteria are not as critical and can be specified as

qualitative statements providing leeway for personal judgement. Many times, the requirements

placed upon a system must be modified during the course of implementing and tuning the

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