Intelligent Motion Systems Modular LYNX System - Manual (Page 36)

1 - 36 Modular LYNX System 12.05.2003
H a l f A x i s O p e r a t i o n ( F o l l o w e r )
In half axis mode the master clock is taken from a clock input 2, 3 or 4 (line pairs 13-14, 15-16 or 17-18) which
have been set for input, clock type and ratio enabled. This is the factor at which the count rate out to the
primary drive will follow the external clock in half axis mode. This clock input would typically be connected
to differential input pairs 15 and 16 (P1, pins 5 – 8). This could be set up as any of the available clock types.
If half axis mode is enabled (HAE), the primary axis of the control will follow the clock input with the ratio
specified by the
HAS variable.
In order to use the HAS (Half axis mode scaling) variable the HAE flag must be set to true (1). For example,
to set the half axis scale factor to .5, where the drive will follow the external Clock input with a ratio of 1
count to the drive for every two counts from the external clock, you would use the command: SET HAS = .5
(or HAS = .5). Figure 6.9 illustrates the connections for using this mode of operation using a clock input
from an encoder.
The sequence of commands used to make this setup function would be as follows:
‘Set IOS 15 to ratio mode
IOS 15 = 5,0,1,0,1,1
‘Set IOS 16 to ratio mode
IOS 16 = 6,0,1,0,1,1
‘Half axis enable set to true
HAE = 1
‘Half axis scaling to .5 (1 output clock pulse to every 2 input clock pulses)
HAS = .5
by a motor mounted encoder. The actual count of encoder pulses received by the Control Module is
maintained by the register
CTR2, (if the encoder is connected to I/O line pair 13 &14) with the EUNIT
variable scaling it to user units. Example:
User Unit (POS) = CTR2 ÷ EUNIT where EE (Encoder Enable) Flag = TRUE(1)
When using the EUNIT scaling factor it is important to understand that you MUST set the EUNIT variable
AND the MUNIT variable to the same scaling factor for accurate position monitoring. In the example below
you will use a hypothetical system designed from the following components:
An IMS IB462H Half/Full Step driver configured for Half Step Operation.
A 1.8° Stepping Motor mounted to a 20cm linear slide.
A 200 Line Encoder.
You will want to use millimeters for our user unit. The IB462H in half step mode will need 400 clock pulses to
turn the motor one revolution. The pitch on the leadscrew is such that one millimeter of linear motion will
require 25 clock pulses. 400 steps/rev ÷ 25 steps/mm = 16 mm/rev. Therefore, you would set the MUNIT
variable as follows:
MUNIT = 400/16
Now, when you give a MOVR 20 instruction, the axis will index 20 millimeters. Now to set the EUNIT
Variable. We have a 200 line encoder connected to a quadrature clock input. This will mean that 1 revolution
will equal 800 Encoder Pulses, you will have to use the same scaling factor as we did for MUNIT as there will
still be 16mm per revolution:
EUNIT = 800/16
Both values must be set, and both must be set to the same scaling factor. With the EE = 1 a MOVR 20
command will still index the axis 20 millimeters, but position will be maintained by CTR2.