HWP PCU Agent
The HWP Phase Compensation Unit (PCU) Agent interfaces with a 8 channel USB relay module (Numato Lab, product Number SKU:RL80001) to apply the discrete phase compensation in 120-degree increments for the HWP motor drive circuit. When used in conjunction with a HWP pid controller, phase compensation in 60-degree increments can be achieved. The HWP PCU can also force the HWP to stop by making the phases of all three-phase motors the same.
usage: python3 agent.py [-h] [--port PORT]
Agent Options
- --port
Path to USB node for the PCU
Dependencies
The PCU device shows up on the system as /dev/ttyACMx where x is not
guaranteed to be consistent. To solve this issue we should create a udev rule
for the PCU device. Establish the udev rule by creating a file in
/etc/udev/rules.d/ with the following contents:
SUBSYSTEM=="tty", ATTRS{idVendor}=="2a19", ATTRS{idProduct}=="0c02", MODE="0666", SYMLINK="PCU"
Note
If multiple PCU devices are connected to the same computer you will want to
include the serial number in the rules, which you can add with
ATTRS{serial}=="<serial number of PCU>".
If the PCU was connected to the computer already you will need to unplug and
replug it for the udev rule to properly recognize the device, create the
symlink, and set the permissions appropriately. Once you complete this step the
device will be recongized on reboot, and the udev rules will not need to be
reinstalled unless you add a new device. The PCU should now be available at
/dev/PCU.
Configuration File Examples
Below are configuration examples for the ocs config file and for running the Agent in a docker container.
OCS Site Config
To configure your HWP PCU Agent for use with OCS you need to add a HWPPCUAgent block to your ocs configuration file. Here is an example configuration block that will automatically start data acquisition:
{'agent-class': 'HWPPCUAgent',
'instance-id': 'hwp-pcu',
'arguments': [['--port', '/dev/HWPPCU'],
['--mode', 'acq']]},
Each device requires configuration under ‘agent-instances’. See the OCS site configs documentation for more details.
Docker Compose
The HWP PCU Agent can (and probably should) be configured to run in a Docker container. An example configuration is:
ocs-hwp-pcu:
image: simonsobs/socs:latest
devices:
- "/dev/HWPPCU:/dev/HWPPCU"
hostname: nuc-docker
environment:
- INSTANCE_ID=hwp-pcu
volumes:
- ${OCS_CONFIG_DIR}:/config:ro
The serial number will need to be updated in your configuration. The hostname should also match your configured host in your OCS configuration file. The site-hub and site-http need to point to your crossbar server, as described in the OCS documentation.
Example Clients
To apply 120-degree phase compensation:
from ocs.matched_client import MatchedClient
hwp_pcu_client = MatchedClient("HWPPCU")
hwp_pcu_client.set_command(command='on_1')
To apply 60 (= -120 + 180) degree phase compensation:
from ocs.matched_client import MatchedClient
hwp_pcu_client = MatchedClient("HWPPCU")
hwp_pid_client = MatchedClient("HWPPID")
hwp_pcu_client.set_command(command='on_2')
hwp_pid_client.set_direction(direction=1)
Agent API
- class socs.agents.hwp_pcu.agent.HWPPCUAgent(agent, port)[source]
Agent to phase compensation improve the CHWP motor efficiency
- Parameters:
agent (ocs.ocs_agent.OCSAgent) – Instantiated OCSAgent class for this agent
port (str) – Path to USB device in ‘/dev/’
- send_command(command)[source]
Task - Send commands to the phase compensation unit. off: The compensation phase is zero. on_1: The compensation phase is +120 deg. on_2: The compensation phase is -120 deg. stop: Stop the HWP spin.
- Parameters:
command (str) – set the operation mode from ‘off’, ‘on_1’, ‘on_2’ or ‘stop’.