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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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In this paper we will discuss the goal we are trying to achieve along with the roadmap for getting there. We will present the products we have produced along with the projects that have baselined these products into their designs. We will finish by discussing our plans for the future.
This paper will present the design of a Current Sense Module (CSM) used to measure motor phase currents that is capable of surviving the harsh ambient environment of ocean worlds, such as Europa and Enceladus. The CSM module is fabricated by i3 Electronics using their Multi-Chip Module (MCM) technology with techniques developed by JPL to allow this module to survive temperatures down to -184°C. This module greatly improves the ability to measure phase and bridge current which can be problematic in extreme environments. In addition, by packaging these electronics at the die level, we achieve significant weight and size savings. This module is one of several modules that employ similar techniques that are integrated into a distributed or centralized motor controller. This paper will discuss the module’s design along with a summary of our test results.
This paper presents work to date in developing, and testing an embedded planar-foil capacitor based interposer intended to be integrated together with high-density components such as Field Programmable Gate Arrays (FPGAs), and Application Specific Integrated Circuits (ASIC). FPGA devices typically have a large number of I/O and power pins. The high speed enabled by these devices requires a large number of discrete bypass capacitors as close as possible to the power pins. These capacitors take up a considerable amount of the board area on the application circuit board. The developed interposer replaces these components freeing up space of traditional bypass capacitors for other circuitry.
This paper will present the application of the Controller Area Network (CAN) for communication between the Motor Control Processor and the Europa Lander Motor Control Cards. The Europa Lander preproject team is concerned about lowering the estimated mass, volume, and power of the mission concept so that it could maximize its science return. The motor controller uses multiple Motor Control Cards to control the 24 motors that will be operating in the extremes of the Europa environment. The CAN bus was considered because of its multi-drop nature, low power interface, and simple communication protocol.
This paper presents our work to date in developing, and testing an embedded planar-foil capacitor based interposer intended to be integrated together with high-density components such as Field Programmable Gate Arrays (FPGAs), and Application Specific Integrated Circuit (ASIC) applications. FPGA devices typically have a large number of I/O and power pins. The high speed enabled by these devices requires a large number of discrete bypass capacitors as close as possible to the power pins. These capacitors take up a considerable amount of the board area on the application circuit board. Our interposer replaces these components freeing up space of traditional bypass capacitors for other circuitry. Our Interposer focuses on the needs of Micro Semi’s RTG4 FPGA. We developed the interposer using COTS embedded foil capacitors. The Interposer is customized to the capacitance requirements for each of the FPGA banks. We evaluated three foil manufactures Oak Mitsui, 3M and TDK. The three different designs were evaluated, but we will focus on the Oak-Mitsui based Interposer that we constructed and tested. Through simulations, we validate the horizontal and vertical interconnect inductances, that FPGA decoupling requirements are met. The use of the interposer results in an overall reduction in our Printed Wiring Board (PWB) area.
This paper will present the application of the Controller Area Network (CAN) for communication between the Motor Control Processor and the Europa Lander Motor Control Cards. The Europa Lander mission is concerned about lowering the mass, volume, and power so that it can maximize its science return. The motor controller uses multiple Motor Control Cards to control the 24 motors that will be operating in the extremes of the Europa environment. The CAN bus was considered because of its multi-drop nature, low power interface, and simple communication protocol. Beyond communication with the motor controller cards we also use the CAN bus interface to gather telemetry from the Power Conversion Card. Our system requires the collection of telemetry at a rate of 64Hz from the Power Conversion Card and all active motor controllers along with the sending of control packets and the receipt of control parameters at 512 Hz. In the paper we will address the ability of the CAN bus to meet these requirements along with our Arduino based test system used to learn about the CAN bus standard and verify our analysis.
JPL is developing a motor controller capable of controlling the motors required for landed missions on icy worlds such as Europa and Enceladus. To support this effort, JPL, together with Tech180, is developing a motor simulator capable of simulating various types of motors required for these missions and their operation in the ambient environment. This system is being designed to support three 3-phase brushless DC motors with the ability to expanded to 24 motors. The simulator is able to simulate motors with current draw up to 10 amps, and sensors that range from resolvers, hall sensors, and encoders. The motor simulator design utilizes NI components and LabVIEW software, along with high-speed FPGA hardware. This paper will present an overview of our motor controller, the requirements for the motor simulator, and details of its design along with the test results to date.
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This paper derives a symbolic multi-body rigid nonlinear model for a space telescope using Stoneking’s implementation of Kane’s method. This symbolic nonlinear model is linearized using Matlab symbolic functions diff and inv because the analytic linearization is intractable for manual derivation. The linearized system model is then used to design the controllers using both linear quadratic regulator (LQR) and robust pole assignment methods. The closed-loop systems for the two designs are simulated using both the rigid model as well as a second model containing flexible modes. The performances of the two designs are compared based on the simulation testing results. Our conclusion is that the robust pole assignment design offers better performance than that of the LQR system in terms of actuator usage and pointing accuracy. However, the LQR approach remains an effective first design step that can inform the selection of real eigenvalues for robust pole assignment. The proposed method may be used for the modeling and controller designs for various multi-body systems.
For the last seven years JPL has been developing motor control electronics for use on future missions to extreme environments such as Europa and Mars. The packaging technology developed will allow the electronics to survive the extremes seen on the surface. This packaging technology allows us to package everything to control a number of motors on a single card including the closed loop control. In order to improve the performance of the motor control we have developed FPGA code to close the position, velocity and current control loops of the motor controller. This code allowed for a significant improvement in loop rate allowing the control of the motors to be more accurate. This allows for more accurate control of descent engines, more precise control of robotic arm motors. In this paper we will present the design of the control algorithm, the performance of the sensors and the test results of the resulting system.
This paper will outline the design and test results for the Europa Lander motor controller’s Power Conversion Slice. Europa Lander is a proposed NASA mission concept to send a stationary spacecraft to Jupiter’s Icy Moon, Europa, to search for subsurface biosignatures. The Power Conversion Card is one of the many technologies designed for this mission. The Power Conversion Card’s primary function is to convert the power supplied by the spacecraft battery to usable power for use within the motor controller. In addition, this card provides power system telemetry to the spacecraft computer. This card tolerates Europa’s harsh radiation environment within a protected vault to enable it to survive the external temperatures which can be as low as -184°C during the three-week mission. This design makes use of multiple commercially available radiation hardened electronics, including Cobham’s UT32M0R500 Arm Microcontroller along with VPT’s DC-DC Converters for power conversion. The microcontroller is used to collect local power system telemetry and assess card health autonomously without intervention from the spacecraft’s main computer. This paper will showcase the design behind the prototype and electrical testing results.
The Large UV/Optical/IR Surveyor (LUVOIR) is a conceptual space observatory under development by NASA Goddard Space Flight Center for the Astronomy and Astrophysics Decadal Survey. As with similar space telescopes, e.g., James Webb, this spacecraft will have ultra-stringent pointing stability requirements, i.e., on the order of miliarcseconds. Thus, the design of the LUVOIR attitude control system (ACS) may benefit from a model-based approach. In this document, we present an approximate model of the LUVOIR composed of two 3D rigid bodies connected by a 1-DOF rotary joint. From this model, we derive the nonlinear equations of motion, following the approach of Eric T. Stoneking [1], and linearize them about an arbitrary reference orientation. Using the subsequent state space representation, it is straightforward to compute a set of control gains (e.g., via the ”lqr” or ”place” commands in MATLAB). We conclude this memo with a comparison of our LQR approach with the existing PID slew controller designed by a former NASA intern.
This document overviews the work I completed in the second half of my summer 2018 internship experience in Code 591 at NASA Goddard Space Flight Center. Please see the former memorandum for additional context on the project. The take away point is that LUVOIR A has been modeled as three rigid bodies linked by 1-DOF rotary joints. An LQR attitude controller was designed for precision pointing of the spacecraft with the design requirement that steady state oscillations have amplitude less than a miliarcsecond. The performance of the algorithm was tested in the Modular Dynamic Analysis Simulink library developed by J. Roger Chen at NASA Goddard. While the initial simulations were of rigid bodies, subsequent simulations included flexible body modes on all three bodies of the model. The simulated structural deformations initially destabilized the LQR controller thus requiring a redesign of the K gain matrix. The final simulation demonstrated a stabilizing feedback gain with miliarcsecond precision within 400 minutes. This run used 20 modes on the spacecraft, 9 on the bus, and 100 on the payload. Future recommended work includes the development of a Vibration Isolation and Precision Pointing System (VIPPS) Simulink model. Armed with this model, the system should be modeled as four bodies whose associated flexible files must be generated from the spacecraft through Gimbal 1, Gimbal 1 through Gimbal 2, Gimbal 2 through the VIPPS interface, and the VIPPS interface through the payload.
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