ZTF Filter Exchanger Controls System D. Hale 2016-04-18

FILTERD FILTER HARDWARE context of where the next two hardware slides fit in

Software Interface to Hardware KUKA Arm TCP/IP socket interface to arm controller commands to and status from controller are transmitted as XML strings status thread is responsible for the I/O function calls

Software Interface to Hardware Arduinos control Electro-Permanent Magnetic (EPM) latches read EPM states read mechanical latch micro-switch states A dedicated Arduino-based microcontroller monitors sensors at each of these physical locations: instrument gripper tool four filter storage slots Arduino Interface A master Arduino handles communication between the Robotic System and each of the six host Arduinos TCP/IP socket interface to master Arduino I2C communication between master and host Arduinos status thread is responsible for the I/O function calls

example command context of where the following slides are going to fit

Commands There are many possible commands that can be recognized by the command thread e.g. exchange_filter(N), stow, instrument, slot, etc. The building blocks of all commands are “primitives” which interface to hardware rigorous unit testing of primitives ensures system reliability

Primitives KUKA Arm Primitives EPM Primitives Sensor Primitives stow slot( N ) instrument check_handoff EPM Primitives engage disengage Sensor Primitives check values These describe all arm movements as specific, pre-defined paths No arbitrary motions means less room for error and more control over safety turns the magnetic latches on and off

Example Command Operations: Check_Status Retrieve Undock Store Dock Fetch Install Stow NB. discrepancy between flowchart boxes and operation list is closet dock/undock not shown

8. Install instrument primitive moves gripper tool carrying filter frame to the instrument EPMs=on and reading no filter latches closed EPMs=on and reading filter describe what’s going on with the sensors

9. Dock EPMs=on and reading filter EPMs=on and reading filter latches open EPMs=on and reading filter EPMs=off describe what’s going on with the sensors

9. Dock check_handoff moves arm a safe distance mechanical latches maintain control until handoff complete, in case of EPM or pawl failure EPMs=on and reading filter latches closed EPMs=on and reading no filter describe what’s going on with the sensors

How are Faults Handled? For every Operation there is defined a set of sensor values required for success Fault / Response / Action table a violation is a fault fault handling is situationally dependent

Fault / Response / Action table Here’s the entire matrix – many possible fault responses and actions to take

Safety The KUKA arm has inherent fault protection and safety features velocity monitor limits kinetic energy workspace monitor limits motion to a defined workspace volume axis range monitor angular limits collision monitor force/torque sensors on each joint

Emergency Stop deactivates drive power and applies brakes trigger sources: strategically placed panic buttons throughout dome door switches telescope tube access doors, filter storage closet doors, etc. limit switches installed on arm

External Limit Switches & Hard Stops hard-stop barriers & limit switch affixed to upper side of axis block affixed to lower side of axis allows some rotation first within boundaries of switch ultimately within hard-stop boundaries

Conclusion control software successful heritage with Robo-AO modularity of the design facilitates testing sub-system testing of lab mock-up will validate operation and fault handling KUKA advantage of mature commercial product local JPL collaborative experience