1. Application-Specific Codesign Platform Generation for Digital Mockups in Cyber- Physical Systems Bailey Miller *, Frank Vahid *†, Tony Givargis † *Dept. Computer Science & Engineering University of California, Riverside {bmiller,vahid}@cs.ucr.edu †Center for Embedded Computer Systems University of California, Irvine givargis@uci.edu This work is supported by the National Science Foundation (CNS1016792) and Semiconductor Research Corporation (GRC 2143.001)

2. Bailey Miller, UC Riverside Testing Cyber-Physical Devices 1/20 It is difficult to test the broad range of environmental conditions for cyber-physical devices Medical devices like ventilators require extensive testing to pass FDA regulations

3. Bailey Miller, UC Riverside Testing via a physical mockup 2/20  Simulate complex environment with mechanical analog

4. Bailey Miller, UC Riverside Testing via a digital mockup 3/20  Simulate complex environment with a mathematical model  Models can simulate dangerous, expensive, or difficult to reproduce scenarios  More accurate than mechanical methods

5. Bailey Miller, UC Riverside Hardware-in-loop testing  Hardware-in-loop not new HiL implementations are ad-hoc and fractured  Hanson, et. al. hardware in loop simulation of cardiovascular system device testing [Medical Engineering and Physics, 2007]  Steurer, PEBB based high-power hardware-in-loop simulation facility for electric power systems  Cai, Design and implementation of a hardware-in-the-loop simulation system for small-scale UAV helicopters.  etc…

6. Bailey Miller, UC Riverside Digital mockup models  Large systems of Ordinary Differential Equations (ODEs) *Gas exchange model: Lutchen et. al. 4/20

7. Bailey Miller, UC Riverside Models in real-time?  Complex models often not real-time 11 generation branching Weibel model (4094 ODEs) 16,49313,880 5/20

8. Bailey Miller, UC Riverside Real-time using FPGAs  FPGAs match model characteristics Fine-grain parallelism Local communication P1P2… P3… … FPGA 6/20

9. Bailey Miller, UC Riverside Digital mockup framework - requirements  A. Flexibility  B. Multi-timing support  C. Co-design Support Processor Model A (1 KHz) Processor Model B (10 Hz) coproc Gas exchange model Respiratory mechanics model 7/20

10. Bailey Miller, UC Riverside Digital mockup framework Digital Mockup (FPGA) Cyber-physical device Processing core Sensor Actuator Device Interface Actuator Models Sensor Models Transducer Bypass – Sirowy, et. al. [International Conference of the IEEE Engineering in Medicine and Biology‘09] Environment Model Interface registers 8/20

11. Bailey Miller, UC Riverside Digital mockup framework - example  1. Device software generates command for actuator Digital Mockup (FPGA) Cyber-physical device Processing core Sensor Actuator Device Interface Actuator Models Sensor Models Environment Model Interface registers 9/20

12. Bailey Miller, UC Riverside Digital mockup framework - example Digital Mockup (FPGA) Cyber-physical device Processing core Sensor Actuator Device Interface Actuator Models Sensor Models Environment Model Interface registers  2. Device interface intercepts command 10/20

13. Bailey Miller, UC Riverside Digital mockup framework - example Digital Mockup (FPGA) Cyber-physical device Processing core Sensor Actuator Device Interface Actuator Models Sensor Models Environment Model Interface registers  3. Actuator model acts on command Outputs of the actuator are registered 11/20

14. Bailey Miller, UC Riverside Digital mockup framework - example Digital Mockup (FPGA) Cyber-physical device Processing core Sensor Actuator Device Interface Actuator Models Sensor Models Environment Model Interface registers  4. The environment model obtains registered actuator outputs and continues to advance model state with new input. Outputs of environment model are registered. 12/20

15. Bailey Miller, UC Riverside Digital mockup framework - example Digital Mockup (FPGA) Cyber-physical device Processing core Sensor Actuator Device Interface Actuator Models Sensor Models Environment Model Interface registers  5. Sensor models obtain registered outputs of environment model 13/20

16. Bailey Miller, UC Riverside Digital mockup framework - example Digital Mockup (FPGA) Cyber-physical device Processing core Sensor Actuator Device Interface Actuator Models Sensor Models Environment Model Interface registers  6. Device interface packages and sends sensor readings to cyber-physical device processing core 14/20

17. Bailey Miller, UC Riverside Digital mockup flexibility  Models map to one or more processors  API for implementing models step(), getSample(), setOutput() Digital Mockup (FPGA) Cyber-physical device Processing core Sensor Actuator Device Interface Actuator Model (proc 1) Sensor Model (proc 2) Environment Model (proc 3) Interface registers void Step() { //airway mechanics model Q = GetSample(FLOW_ADDR); Pv += (Q/Ct-Pv/((Rl+Rt)*Ct) + Pl/((Rl+Rt)*Ct )) *dt; Pc = Pv*(Rl/(Rt+Rl))+Pl*(Rt/(Rl+Rt)); Pl += (Pv/(Cl*(Rl+Rt))-Pl/(Cl*(Rl+Rt)))*dt; SetOutput(PRESSURE_ADDR,Pc); } void Step() { //Gas exchange model Q = GetSample(FLOW_ADDR); F = (Q-Pl)/R; Vl += F*dt; dVl/DPl += C*dt; C_lung = Q_lung/Vl; k = ln(Vmax/Vmin)/a; Q_lung = C_air + (C_lung-C_air)*exp(-k*t); SetOutput(PRESSURE_ADDR,Pc); SetOutput(CONCENTRATION_ADDR, Q_lung); … } 15/20

18. Bailey Miller, UC Riverside Digital mockup multi-timing support  Models may be solved at different time steps Models need not be synchronized  Update interface registers after each time step to ensure up-to-date data is available Digital Mockup (FPGA) Device Interface Actuator Model Sensor Model Environment Model 16/20 Interface registers

19. Bailey Miller, UC Riverside Digital mockup co-design support  3. Co-design Support Digital Mockup (FPGA) Device Interface Actuator Model Sensor Model Environment Model coproc controller Environment Model Coprocessor Step() { //processor hosts interface to coproc WriteCoprocessor(COPROCESSOR_FLOW_ADDR, getSample(FLOW_ADDR)); StepCoprocessor(); SetOutput(ReadCoProcessor(PRESSURE_ADDR)); } StepCoProcessor: process(clock_i) begin case state is when ‘0’ => step_done_o <= ‘0’; if (step_i = ‘1’) then state <= ‘1’; end if; when ‘1’ => model_start <= ‘1’; --model omitted for brevity if (model_done=’1’) then step_done_o <= ‘1’; end if; end case; end process; ReadCoprocessor: process(read_enable_i) if (read_enable=’1’) then case address_i is when “00000000” => data_o <= pressure_register; when “00000001” => data_o <= weibel_gen0_volume; … end case; end if; end process; WriteCoprocessor: process(write_enable_i) if (write_enable=’1’) then case address_i is when “00000001” => flow_register <= data_i; … end case; end if; end process; 17/20

20. Bailey Miller, UC Riverside Digital mockup generator tool  Automatically generates templates for digital mockup framework  Select platform type, transducer information, enable coprocessor support, etc. ~~~~~~~~~ C++, VHDL templates 18/20

21. Bailey Miller, UC Riverside Digital mockup generator tool  Generated digital mockup using tool Initially, simple model implemented (3 ODEs) on processor only ~2 hours to build new digital mockup test setup  Swapped simple lung model with bifurcating model (100+ ODEs) for enhanced accuracy. < 5 minutes to perform swap (cut/paste operation and adding of coprocessor C++ interface code.) Item#C lines #VHDL lines Generated interface templates 221112 Simple lung model65N/A Device interface1971987 Total4702497 Item#C lines #VHDL lines Generated interface templates 221112 Bifurcating Weibel model257350 Device interface1971987 Total42210199 19/20

22. Bailey Miller, UC Riverside Conclusions  Digital Mockups enhance testing of cyber-physical device software FPGAs allow complex physiological models to run in real-time  Proposed framework and tool to guide design of digital mockup test setups Supports model flexibility and co-design capability Shortens time spent on testing of cyber-physical devices Promotes clean and consistent digital mockup implementations Digital mockup (FPGA) Lung model Ventilator Cyber-physical device Pacemaker Heart model Satellite orbital physics 20/20