CDS3310

Analog Inputs

The CDS-3310 has two analog inputs configured for the range between 0V and 5V. The inputs are decoded by a 12-bit A/D decoder giving a voltage resolution of approximately 1 mV (a 16-bit A/D is available on the DB-28040). The impedance of these inputs is effectively infinite. The analog inputs are read with @AN[x] where x is a number 1 thru 2.

Digital Inputs

The general use inputs are TTL and are labeled DGTL IN 1 to DGTL IN 8 on the silkscreen on the

sheet metal. These inputs can be interrogated with the use of the command TI (Tell Inputs), the

operand _TI, and the function @IN[n] (see Chapter 7, Mathematical Functions and Expressions).

Digital input 8 can accept a differential (two-wire) signal. To connect a single-ended (one wire) signal, connect to DGTL IN 8+ and leave DGTL IN 8- disconnected.

Analog Output

The CDS-3310 has one analog output configured for the range between -10V and 10V. The output is driven by a 16-bit D/A converter giving a voltage resolution of approximately 300 μV. The analog output is set with AO command.

Communication Protocols

Ethernet communication transfers information in ‘packets’. The packets must be limited to 470 data bytes or less. Larger packets could cause the controller to lose communication. Communication protocols are necessary to dictate how these packets are sent and received. Although UDP/IP is more efficient and simple, Galil recommends using the TCP/IP protocol. TCP/IP insures that if a packet is lost or destroyed while in transit, it will be resent. When using TCP/IP, each master or slave uses an individual Ethernet handle. The term “Master” is equivalent to the internet “client”. The term “Slave” is equivalent to the internet “server”.

Controller Response to Commands

Instructions are sent in ASCII, and the CDS-3310 decodes each ASCII character (one byte) one at a time. It takes approximately 0.5 msec for the controller to decode each command. After the instruction is decoded, the CDS-3310 returns a response to the port from which the command was generated. If the instruction was valid, the controller returns a colon (:) or a question mark (?) if the instruction was not valid. For example, the controller will respond to commands which are sent via the main RS-232 port back through the RS-232 port, and to commands which are sent via the Ethernet port back through the Ethernet port.

For instructions that return data, such as Tell Position (TP), the CDS-3310 will return the data followed by a carriage return, line feed and colon. It is good practice to check for : after each command is sent to prevent errors.

Command Syntax – ASCII

CDS-3310 instructions are represented by two ASCII upper case characters followed by applicable arguments. A space may be inserted between the instruction and arguments. A semicolon or <return> is used to terminate the instruction for processing by the CDS-3310 command interpreter. Commands will not be processed until an <return> command is given.

Programming Motion

Independent Axis Positioning

Absolute or relative positioning where each axis is independent and follows prescribed velocity profile.

The user specifies the desired absolute position (PA) or relative position (PR), slew speed (SP),

acceleration ramp (AC), and deceleration ramp (DC), for each axis.

The speed (SP) and the acceleration (AC) can be changed at any time during motion, however, the deceleration (DC) and position (PR or PA) cannot be changed until motion is complete. Remember, motion is complete when the profiler is finished, not when the actual motor is in position. The Stop command (ST) can be issued at any time to decelerate the motor to a stop before it reaches its final position. An incremental position movement (IP) may be specified during motion as long as the additional move is in the same direction. Here, the user specifies the desired position increment, n. The new target is equal to the old target plus the increment, n. Upon receiving the IP command, a revised profile will be generated for motion towards the new end position. The IP command does not require a BG.

Independent Jogging

Velocity control where no final endpoint is prescribed, speed, direction and acceleration can be changed during motion. Motion stops on Stop command. An instant change to the motor position can be made with the use of the IP command. Upon receiving this command, the controller commands the motor to a position which is equal to the specified increment plus the current position.

Position Tracking

Supports changing the target of an absolute position move on the fly. New targets may be given in the same direction or the opposite direction of the current position target. The controller will then calculate a new trajectory based upon the new target and the acceleration, deceleration, and speed parameters that have been set.

Contour Mode

Allows the user to generate custom profiles by updating the reference position at a specific time rate. In this mode, the position can be updated randomly or at a fixed time rate, but the velocity profile will always be trapezoidal with the parameters specified by AC, DC, and SP. Updating the position target at a specific rate will not allow the user to create a custom profile.

Dual Loop (Auxiliary Encoder)

The most common use for the second encoder is backlash compensation, position encoders are mounted on both the motor and the load. The continuous dual loop combines the two feedback signals to achieve stability. This method requires careful system tuning, and depends on the magnitude of the backlash. However, once successful, this method compensates for the backlash continuously.

The second method, the sampled dual loop, reads the load encoder only at the end point and performs a correction. This method is independent of the size of the backlash. However, it is effective only in point-to-point motion systems which require position accuracy only at the endpoint.

Motion Smoothing

The CDS-3310 controller allows the smoothing of the velocity profile to reduce the mechanical vibration of the system.

Trapezoidal velocity profiles have acceleration rates which change abruptly from zero to maximum value. The discontinuous acceleration results in jerk which causes vibration. The smoothing of the acceleration profile leads to a continuous acceleration profile and reduces the mechanical shock and vibration.