Tesla Motors
  • Palo Alto, United States
Recent publications
Capacitor voltage natural balancing is an attractive feature of flying capacitor multilevel (FCML) converters. However, with the commonly used phase-shifted pulsewidth modulation, the capacitor voltages still can deviate, and active balancing is often required. Although the natural balancing mechanism and its dynamics have been extensively studied in existing literature, some sources that are responsible for capacitor imbalance in engineering practice are still unclear. This article experimentally investigates the origins of the voltage imbalance in practical implementations of such converters. It presents the corresponding circuit analysis as well as solutions that improve balancing. It is shown that the source impedance and the input capacitance can greatly deteriorate capacitor balancing. Moreover, we also demonstrate in theory and with experiments that an FCML converter with an even number of levels inherently has stronger immunity to such disturbance than that with an odd number of levels. It is also found that the gate signal propagation delay mismatch in half-bridge gate drivers can lead to capacitor imbalance, and this problem is addressed by an alternative gate drive power supply design. Finally, the variations of on -state resistance among different switches are found to have a relatively small impact on capacitor voltage balancing.
We observe that between the competitors of technology products, companies such as HP and Xerox or Apple and Google, one competitor (HP and Apple) manages the reverse supply chain to extract value profitably, while the other competitor (Xerox and Google) uses a third-party reverse logistics company to simply recycle consumer returns. In this chapter, we show that, under a given set of supply chain levers, the OEM’s approach to supply chain network design can significantly impact the profitability in the reverse supply chain over the product lifecycle. We propose an integrated multi-period optimization model called the product life cycle optimization model (PLCOM) to design the closed loop supply chain (CLSC) for the OEMs. The PLCOM is a mixed-integer linear program that consists of a demand model based on the extended-Bass’s diffusion model and a pricing model based on a realistic customer willingness to pay (WTP). The PLCOM is applied to a realistic case study using Apple’s iPhone 7 for a product life cycle of 8 years. We show that an integrated approach to designing the supply chain network by the OEMs is more profitable compared to a sequential approach.
Tesla's Full Self Driving (FSD) computer is the world's first purpose-built computer for the highly demanding workloads of autonomous driving. It is based on a new SoC which integrates industry standard components like CPUs, ISP and GPU, together with our custom neural network accelerators. The FSD computer is capable of processing up to 2,300 frames per second, a 21x improvement over Tesla's previous hardware and at a lower cost, and when fully utilized, enables a new level of safety and autonomy on the road.
In this paper, a new analytical method is proposed to estimate eddy currents inside linear conductive materials. The novel closed form formulation takes into account the effects of both the conductor reaction field which dominates at high frequencies as well as the spatially non-homogeneous nature of the magnetic field penetrating the material. Although the model is suitable for most kinds of permanent magnet machines, it is particularly useful for surface mounted permanent magnet machines where both of these phenomena are prominent. The numerical implementation of the proposed model, which consists of a combination of the method of images and 4-D Fourier transform, is presented. The model is then validated against 2-D and 3-D FEM for a simple magnetic circuit, showing good agreement. Finally, the eddy current magnet loss in a surface-mounted permanent magnet synchronous machine is evaluated and results are discussed.
We are proud to bring to you an issue focused on a pertinent topic-new mobility. The term new mobility was coined to represent four pivotal technologies that will change how we move not only ourselves but also our cargo: connected cars, autonomy, shared mobility, and electrification. The acronyms CASE or ACES are often used to convey these traits that new mobility entails.
Overview of distributed energy storage for demand charge reduction - Volume 5 - Said Al-Hallaj, Greg Wilk, George Crabtree, Martin Eberhard
This paper demonstrates a two-stage implementation of a step-down power factor preregulator design that achieves a high efficiency across the entire universal input voltage range (85-265 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> ) for an offline power supply application. In this implementation, a resonant LLC converter supplies power to a boost converter operating in a continuous conduction mode. A variable frequency multiplier technique is used in a resonant LLC converter stage to provide different dc gains and compress the effective input voltage range. The efficiency performance achieved is flatter and higher than other conventional offline power converter design consisting of a boost power factor correction circuit followed by a resonant LLC converter, whose efficiency tends to drop significantly at low-line input voltages. The proposed circuit allows MOSFETs with lower voltage ratings and better conduction/switching characteristics to be used in both converter stages. Both of the LLC stage and boost circuit can be better optimized due to the compressed operation range and better semiconductor switches. A scaling law of power losses versus breakdown voltage requirement for boost circuit under the condition of the same output power is presented. Experimental results demonstrated a flatter high efficiency performance across a wide input range.
By 2050, it's normal that the total populace will contact 9.2 billion individuals, 34 percent higher than today. A lot of this development will occur in creating nations like India, which has the biggest zone on the planet with arable land for agriculture. To stay aware of rising populaces and wage development, worldwide sustenance generation must increment by 70 percent so as to have the capacity to encourage the world. With help of IoT, control focuses gather and process information continuously to enable ranchers to settle on the best choices as to planting, treating and collecting crops. Sensors set all through the fields are utilized to gauge temperature and stickiness of the dirt and encompassing air. We Propose a Cloud based Irrigation System for better agriculture farming.
Prolonged mechanical loading can lead to the breakdown of skin and underlying tissues which can, in turn, develop into a pressure ulcer. The benefits of pressure relief and/or redistribution to minimise risk have been well documented. Manufacturers have developed alternating air pressure mattresses (APAMs) to provide periodic relief for individuals on prolonged bed-rest. The present study describes the development of a control system, termed Pneumatic Manager which can vary the signature of an APAM, namely its pressure amplitude, cell profile and cycle period. An experimental array was designed to investigate the effects of varying these parameters, particularly with respect to its ability to maintain skin viability in a group of five healthy volunteers lying in a supine position. Transcutaneous gas (TcPO2/TcPCO2) tensions at the sacrum were monitored. In addition, pressures and microclimate parameters at the loaded support interface were also measured. In the majority of test conditions the alternating support produced sacral TcPO2 values, which either remained relatively high or fluctuated in concert with cycle period providing adequate viability. However, in 46% of cases at the extreme pressure amplitude of 100/0 mmHg, there was compromise to the skin viability at the sacrum, as reflected in depressed TcPO2 levels associated with an elevation of TcPCO2 levels above the normal range. In all cases, both the humidity and temperature levels increased during the test period. It is interesting to note that interface pressures at the sacrum rarely exceeded 60 mmHg. Although such studies need to be extended to involve bed-bound individuals, the results provide a design template for the optimum pressure signatures of APAM systems to ensure maintenance of skin viability during pronged loading.
This chapter will introduce and discuss important system-level challenges for software-defined networking (SDN) in fiber wireless networks, particularly in light of recent networking trends such as 5G mobile networks and the Internet of Things (IoT) paradigm. The presented discussion will cover vital aspects from both the control and data plane perspectives. In the data plane, recent fiber wireless trends surrounding the increasingly strong reliance of advanced mobile systems on fiber-optic networks and the emergence of cloud radio access network architectures with fiber-optic links to/from remote wireless cell sites will be covered in particular detail. Specifically, the high-speed, low-latency optical fronthaul architecture will be regarded as the baseline for future fiber wireless networks, and system-level challenges related to signaling formats, network densification and topology, and optical component selection will be considered. Moreover, the requirements for and ramifications of SDN-based control in fiber wireless networks will be examined. A survey of recent R&D advances in SDN for fiber wireless will also be presented. As potential solutions to important system-level challenges, efficient signaling across the optical network, flexibility in the selection of wavelength division multiplexing (WDM)-based optics components, and support for a dynamic physical-layer topology will be highlighted. In terms of network control and management, a centralized, programmable SDN-based control plane is regarded as an attractive approach to bring about a fiber wireless network evolution featuring automated, programmable end-to-end resource orchestration and ultimately a high quality-of-experience (QoE) for end users.
Not every company can afford or is willing to invest in long-term life testing due to time and cost constraints. But such a test can provide very valuable insight about product field behavior during its lifetime. Authors of this paper present a case study on hard disk drive long-term life test data analysis. In order to deal with the non-monotonic hazard rate behavior, the bi-modal mixed life distribution and bi-modal competing failure modeling are applied to fit the time to failure data. The model parameters’ estimation, their physical implications, and field long-term reliability predictions using these two approaches are discussed and compared. The recommendations are given regarding the applicability of each model from an engineering application perspective.
Different battery chemistries perform better on different axes, such as energy density, cost, peak power, recharge time, longevity, and efficiency. Mobile system designers are constrained by existing technology, and are forced to select a single chemistry that best meets their diverse needs, thereby compromising other desirable features. In this paper, we present a new hardware-software system, called Software Defined Battery (SDB), which allows system designers to integrate batteries of different chemistries. SDB exposes application programming interfaces (APIs) to the operating system, which controls the amount of charge flowing in and out of each battery, enabling it to dynamically trade one battery property for another depending on application and/or user needs. Using microbenchmarks from our prototype SDB implementation, and through detailed simulations, we demonstrate that it is possible to combine batteries which individually excel along different axes to deliver an enhanced collective performance when compared to traditional battery packs.
This work presents a series of DNA-structured linear actuators that have high displacements and compact profiles. These actuators operate by twisting and untwisting a double helix that resembles a DNA molecule. Unlike most similarly-motivated twisted string actuators (TSAs), these DNA-structured actuators can have the ability to exert both push and pull forces on a load. Thus, although originally designed for cable-driven robotics, these actuators have the ability to work as part of many different mechatronic systems. Two inherently different actuator designs were investigated, one with straight-line edges (rails) and one with helical rails. Two mathematical models of angular rotation versus linear displacement were developed and simulated, one for each design, and three prototypes were constructed to validate the models. The final prototype was tested for displacement, restorative torque, and pull force characteristics. This last prototype showed a 30.5 cm stroke for a 40.5 cm actuator, or a displacement of 75.3% of its total length. Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
We present a high-heat-flux cooling device for advanced thermal management of electronics. The device incorporates nanoporous membranes supported on microchannels to enable thin-film evaporation. The underlying concept takes advantage of the capillary pressure generated by small pores in the membrane, and minimizes the viscous loss by reducing the membrane thickness. The heat transfer and fluid flow in the device were modeled to determine the effect of different geometric parameters. With the optimization of various parameters, the device can achieve a heat transfer coefficient in excess of 0.05 kW/cm²-K, while dissipating a heat flux of 1 kW/cm². When applied to power electronics, such as GaN high-electron-mobility transistors, this membrane-based evaporative cooling device can lower the near-junction temperature by more than 40 K compared with contemporary single-phase microchannel coolers.
This paper presents the design and development of an automated steering control system that has been successfully deployed on an 18.3-m (60-ft) articulated bus for revenue service in a bus rapid transit line in Eugene, OR, USA, between June 2013 and May 2015. This automated steering system provides both lane keeping and S-curve precision docking on 4-km-long narrow and curving urban segments with six stations and mixed traffic lanes while the operator controls the speed. The objective of deploying an automated bus that carries passengers for an extensive period of time elevated the system safety and performance requirements. This paper describes three key elements in the controller design that address the safety and performance challenges, i.e., high precision, fault tolerance, and control transitions. The experience of designing and deploying such a system in revenue service helps advance the field of automated vehicle by directly addressing its safety issues as an integral part of the automated vehicle control system design.
This paper presents findings based on the examination of time-series tire pressure data. Tire pressure is important to vehicle safety due to its effects on vehicle handling and stability, as well as the impact that inappropriate tire pressure has on tire wear and tire failures. Previous research such as NHTSA’s 2001 Tire Pressure Special Study sampled vehicle populations and recorded tire pressures at a single point in time. Such studies yield important insights into tire pressures on individual vehicles and across the vehicle populations, but cannot provide insights into the behavior of tire pressures over time. The data presented in this paper was measured using the tire pressure monitoring system (TPMS) data from Tesla Model S vehicles. Using Tesla’s on-board diagnostic data logging and remote data retrieval capabilities, the time history of each vehicle’s tire pressures was recorded and fleet-wide data was analyzed. The resulting analysis provides insights into tire pressure changes caused by permeation and slow leaks as well as temperature fluctuations at both drive-cycle and seasonal time scales. The paper also includes examples of tire punctures with resulting pressure data.
This paper proposes a model of a single-phase bidirectional electric vehicle (EV) charger with capability of operating in all four quadrants of the P-Q plane. The steady-state and step responses of the proposed model are used to validate it, based on the actual responses of a bidirectional charger prototype for different P-Q requests. The model can be used efficiently in time-domain simulations that require models of a number of EV chargers, such as EV integration studies in low-voltage (LV) distribution networks. A practical case study is presented to demonstrate and test the proposed smart charger and model, investigating the provision of vehicle-to-grid (V2G) for active and reactive power in an LV residential distribution network. These results demonstrate the advantages of the presented charger model for developing V2G strategies in distribution networks.
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Minos Beniakar
  • EM Motor Design Team
Bozhi Yang
  • Electric Vehicle Powertrain Development, Smart Car, New Energy Car
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