A multi-mode wide-range composite motor system and a control method thereof

Abstract

This invention discloses a multi-mode wide-range composite motor system and its control method for electric vehicles. The system employs a coaxial integrated composite rotor structure, rigidly fixing the permanent magnet synchronous section and the torque compensation section axially, with a magnetic circuit isolation structure in between, and correspondingly setting two sets of independently controlled stator windings. The core innovation of this invention lies in the system architecture: the torque compensation section can act as a near-zero-loss inertial flywheel during high-speed cruising, eliminating the ineffective losses caused by idle motors; simultaneously, the permanent magnet synchronous section provides a stable operating benchmark for the torque compensation section (especially the synchronous reluctance motor), systematically suppressing its inherent weaknesses, allowing it to operate smoothly without complex optimization. This system achieves efficient operation and power redundancy under all working conditions, providing a technical foundation for vehicle lightweighting and cost reduction.

Description

Technical Field

[0001] This invention relates to the field of electric drive system technology for new energy vehicles, specifically to a composite motor system that integrates a permanent magnet synchronous motor and a torque compensation motor axially, and its intelligent collaborative control method. Background Technology

[0002] Currently, there are prominent technical contradictions in the process of adapting electric vehicle drive systems to achieve high performance across a wide speed range.

[0003] First, single-type motors have inherent performance limitations. Permanent magnet synchronous motors are highly efficient and have high power density, but their low-speed torque output capability is limited. Furthermore, at high speeds, continuous field weakening control is required to maintain voltage balance, resulting in additional copper and iron losses, which leads to a decrease in efficiency at high speeds. While a dual-motor solution with a split-shaft arrangement (such as a combination of an asynchronous motor on the front axle and a permanent magnet motor on the rear axle) can balance high and low-speed performance, it increases the complexity of the transmission mechanism, the weight of the vehicle, and production costs. Moreover, when one set of motors is not working, its rotor and related components will experience ineffective coasting losses, becoming an additional source of mechanical resistance and wasting system efficiency.

[0004] Secondly, high-performance motors such as synchronous reluctance motors have inherent drawbacks when used alone. While synchronous reluctance motors have simple rotor structures and low costs, they exhibit significant torque ripple during operation, easily leading to vibration and noise. Furthermore, their strong nonlinear characteristics place high demands on high-precision control algorithms. Existing technologies often address these issues by optimizing rotor magnetic barrier shapes (such as eccentric circles, asymmetric or complex curved magnetic barrier structures) or developing complex control strategies. However, this not only increases design and manufacturing costs but also fails to address the inherent limitations of their standalone applications at the architectural level.

[0005] In addition, some existing coaxial combined motor solutions (such as patent document CN102684437A) only use the asynchronous motor as the starting component of the permanent magnet synchronous motor. The function is limited and the adaptability to operating conditions is poor. After starting, the auxiliary motor cannot participate in dynamic power adjustment and energy efficiency optimization under all operating conditions, which makes it difficult to meet the continuously changing driving conditions of electric vehicles.

[0006] Therefore, there is an urgent need in this field for a new system-level motor architecture that can avoid the performance shortcomings of a single motor, eliminate the ineffective losses of multi-motor split-shaft arrangement, and enable high-performance, cost-effective motors such as synchronous reluctance motors to stably adapt to the high-performance, wide-speed-range, and high-efficiency drive requirements of new energy vehicles without complex structural optimization. Summary of the Invention

[0007] (a) Technical problems to be solved This invention aims to systematically solve the problems at multiple levels described in the background section above: This addresses the contradiction between high-speed field weakening losses and insufficient low-speed torque in a single permanent magnet synchronous motor.

[0008] Eliminate the inherent energy waste problem in split-shaft dual-motor systems where "idle motors become resistance sources or ineffective coasting losses".

[0009] A system architecture is provided that enables torque compensation units such as synchronous reluctance motors to avoid their inherent weaknesses without relying on complex body structure optimization and independent high-precision control strategies, thus achieving stable, efficient, and low-cost applications.

[0010] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: A multi-mode wide-range composite motor system has a coaxial integrated composite rotor as its mechanical core. This rotor rigidly fixes the rotor cores of the permanent magnet synchronous operating section and the torque compensation operating section to the same shaft, with an axial magnetic circuit isolation structure between the two sections. The permanent magnet synchronous operating section uses low-remanence, lightweight flux permanent magnets to physically optimize high-speed performance. The stator side has two electrically independent sets of first and second stator windings.

[0011] The torque compensation section can be implemented as a technologically mature asynchronous induction motor section, or as a synchronous reluctance motor section with cost and supply chain advantages. When using a synchronous reluctance motor section, its rotor structure can directly adopt the conventional multi-layer symmetrical magnetic barrier topology in the field (e.g., standard multi-layer V-shaped or arc-shaped magnetic barriers), without the need for any specific optimized shape involving patent risks.

[0012] The key to this invention lies in the "master-slave collaboration" effect brought about by the system architecture. Because the permanent magnet synchronous section and the torque compensation section are rigidly connected through the composite rotor, the highly stable and continuous sinusoidal rotating magnetic field and precise mechanical angular position established by the permanent magnet synchronous section during operation provide a slip-free synchronous operating reference for the torque compensation section (especially the synchronous reluctance motor section). This architecture fundamentally changes the working environment of the torque compensation section: For the synchronous reluctance motor segment, its inherent torque ripple and nonlinearity are systematically averaged and suppressed by the stable main magnetic field and mechanical constraints. Its rotor does not need to independently cope with stability challenges, but is "pulled" to operate in a near-ideal state.

[0013] For the entire system, when only the permanent magnet synchronous section needs to work alone (such as high-speed cruising), the winding of the torque compensation section can be completely de-energized. At this time, thanks to the effect of the axial magnetic circuit isolation structure, its rotor, driven by the permanent magnet section rotor, rotates coaxially as an inertial flywheel with almost zero electromagnetic loss, thus completely transforming the "burden" in the traditional solution into a "system asset".

[0014] The system can intelligently judge based on real-time vehicle speed, required torque and driving intention signals by independently controlling the dual windings, and seamlessly switch between various working modes such as low speed high torque, efficient cruise, coordinated energy recovery and power assistance.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention has the following outstanding advantages: Avoiding magnetic field weakening losses at the source and achieving high efficiency across the entire range: By adopting a lightweight magnetic flux permanent magnet design, the need for continuous magnetic field weakening control in the high-speed range is greatly reduced or eliminated from a physical perspective, directly improving high-speed cruising efficiency, while also making up for the shortcomings of insufficient low-speed torque of a single permanent magnet synchronous motor.

[0016] Turning burdens into assets and eradicating systemic waste: Through coaxial rigid connection and magnetic circuit isolation design, the torque compensation section rotor that is powered off during cruise is transformed into a low-loss inertial flywheel, fundamentally solving the long-standing industry problem that "the non-working motor must be a source of resistance" in the split-shaft dual-motor scheme, and realizing the essential optimization of energy flow.

[0017] Endogenous synergistic stability, liberating component design: This invention provides a system-level technical approach. For the synchronous reluctance motor section, its stable and smooth operation is not achieved through complex optimization of itself, but is guaranteed by the architectural advantages provided by the permanent magnet synchronous section. This allows the use of the simplest and lowest-cost conventional design to meet the requirements of high-performance applications, breaking away from the traditional mindset of "optimizing components to compensate for defects," and producing unexpected technical effects.

[0018] Achieving a system-level positive design cycle: Because this system achieves high efficiency across a wide speed range and high instantaneous torque redundancy within a single unit, it brings optimization to the design paradigm for OEMs. While meeting the same vehicle performance targets, it significantly reduces the excessive redundancy design requirements for drive motor peak power, battery pack capacity, and peak discharge rate (C-rate), directly addressing the core cost and weight bottlenecks of electric vehicles, and helping to achieve a positive cycle of vehicle weight reduction, energy consumption reduction, and range improvement. Attached Figure Description Figure 1 A schematic diagram of the axial cross-section of a coaxial multimode wide-range composite motor; Figure 2 The logic control flowchart for intelligent switching of working modes. In the diagram: 1-composite rotor, 11-permanent magnet synchronous working section, 12-torque compensation working section, 13-axial magnetic circuit isolation structure, 2-first stator winding, 3-second stator winding, 4-shaft. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to explain the present invention and are not intended to limit the present invention. like Figure 1 As shown, in this embodiment of the multi-mode wide-range composite motor system, the composite rotor 1 is rigidly fixed to the rotating shaft 4 by means of interference fit and key pins, consisting of a permanent magnet synchronous working section 11 and an asynchronous induction working section 12 (i.e., a specific form of torque compensation working section). An appropriate axial clearance is left between the two rotor core sections to form a magnetic circuit isolation structure 13, and an annular spacer made of aluminum alloy can be optionally installed to enhance the magnetic shielding effect.

[0020] The permanent magnet synchronous operating section 11 uses low-remanence neodymium iron boron permanent magnets (e.g., grade N35UH), with a magnetic flux designed to be approximately 60%-70% of that of conventional motors. The rotor of the asynchronous induction operating section 12 is a cast aluminum squirrel cage structure. The stator slots are respectively embedded with a first stator winding 2 and a second stator winding 3 that are completely independent in the circuit.

[0021] The system operates according to the vehicle control unit (VCU) or integrated motor controller. Figure 2 The logic shown is used for management: Low-speed, high-torque mode: When the vehicle starts, climbs a hill, or the required torque exceeds a set threshold (e.g., 60% of the rated torque), the controller simultaneously supplies power to the first and second windings (2, 3). The permanent magnet synchronous section 11 and the asynchronous induction section 12 jointly output torque, perfectly compensating for the torque gap of the permanent magnet section in the low-speed range.

[0022] High-efficiency cruise mode: When the vehicle speed increases to the high-efficiency range (e.g., >70km / h) and the required torque is stable, the controller only supplies power to the first winding 2. The permanent magnet synchronous section 11 operates efficiently with its preset low magnetic flux, without the need for magnetic weakening. The second winding 3 is de-energized, and the rotor of the asynchronous section 12 is dragged as an inertial flywheel under magnetic circuit isolation, with extremely low wind friction and residual eddy current losses.

[0023] Collaborative energy recovery mode: When the vehicle decelerates or goes downhill, the controller energizes the second winding 3, enabling the asynchronous section 12 to provide precise and controllable braking or driving force; at the same time, it controls the first winding 2 to be in the power generation state, efficiently recovering energy to the battery.

[0024] Power Assist Mode: During cruise, if the controller detects an intention to accelerate rapidly (such as a change rate of throttle pedal opening exceeding 100% / second), it will instantly connect the second winding 3, and the asynchronous segment 12 will quickly provide auxiliary thrust. After completion, it will return to its original state. The main difference between this embodiment and Embodiment 1 is that the torque compensation working section 12 is specifically implemented as a synchronous reluctance motor section. Its rotor is made of well-known, classic multi-layer (e.g., 4-layer) symmetrical V-shaped magnetic barrier silicon steel sheets, a common textbook design without any special shape optimization. The stator side configuration, winding independence, and power control mode are the same as in Embodiment 1.

[0025] In this embodiment, the synergistic advantages of the system architecture are particularly evident: Stability stems from the rigid connection between the rotor of the synchronous reluctance section 12 and the rotor of the permanent magnet synchronous section 11, ensuring that their speed and angular position are strictly locked. The stable sinusoidal rotating magnetic field generated by the permanent magnet section 11 provides a natural, delay-free, and precise reference for the dq-axis magnetic field orientation control of the reluctance section 12. Its inherent torque ripples are mechanically averaged macroscopically and smoothed microscopically by the main magnetic field, thus eliminating the need for independently designing complex torque ripple suppression algorithms or vibration control strategies.

[0026] Simplified control: Since the rotor position and speed information of the reluctance section 12 can be obtained directly from the control system of the permanent magnet section 11 (or shared through the same sensor), its control complexity is greatly reduced. Its control objective is simplified from "maintaining its own stable operation" to "outputting the required compensation torque under a given reference".

[0027] Flywheel status: In high-efficiency cruise mode, the windings of synchronous reluctance section 12 are de-energized. Its rotor is a pure silicon steel sheet laminate with no winding conductors. Under magnetic circuit isolation, the iron loss when the flywheel is idling is extremely small, making it a more ideal choice for achieving "zero-loss assets".

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. For example, the specific dimensions of the magnetic circuit isolation structure 13, the specific grade of the permanent magnet, and the specific threshold for mode switching can all be adjusted according to the actual vehicle model and performance requirements. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-mode wide-range composite motor system, characterized in that, include: The coaxial integrated composite rotor consists of a permanent magnet synchronous working section and a torque compensation working section. The rotor of the torque compensation working section can rotate coaxially with the rotor of the permanent magnet synchronous working section. An axial magnetic circuit isolation structure is provided between the permanent magnet synchronous working section and the torque compensation working section; A first stator winding and a second stator winding, which are electrically independent of each other and are respectively arranged in the axial direction corresponding to the two working sections; When the second stator winding is de-energized, the rotor of the torque compensation working section can rotate coaxially with the rotor of the permanent magnet synchronous working section as an inertial body.

2. The system according to claim 1, characterized in that, The torque compensation working section is the asynchronous induction motor section.

3. The system according to claim 1, characterized in that, The torque compensation working section is the synchronous reluctance motor section.

4. The system according to claim 3, characterized in that, The rotor of the synchronous reluctance motor section adopts a multi-layer symmetrical magnetic barrier topology.

5. The system according to any one of claims 1 to 4, characterized in that, The permanent magnet synchronous working section uses a light flux permanent magnet with low remanence.

6. The system according to claim 5, characterized in that, The magnetic flux design value of the light flux permanent magnet ensures that the motor system does not require continuous field weakening control when operating at its rated maximum speed.

7. The system according to any one of claims 1 to 6, characterized in that, The axial magnetic circuit isolation structure is an air gap formed between the rotor cores of the two working sections, or a non-magnetic metal sleeve filled in the gap.

8. A method for controlling a multi-mode wide-range composite motor system as described in any one of claims 1 to 7, characterized in that, include: (1) Low speed and high torque mode: In response to the demand torque being greater than the first threshold, the first stator winding and the second stator winding are simultaneously energized; (2) High-efficiency cruise mode: In response to the speed being higher than the second threshold and the required torque being stable, the control only energizes the first stator winding, so that the rotor of the torque compensation working section can idle as an inertial body; (3) Cooperative energy recovery mode: In response to deceleration or downhill conditions, the second stator winding is energized to provide controllable electromagnetic force, while the first stator winding is energized to generate electricity.

9. The method according to claim 8, characterized in that, Also includes: Power Assist Mode: In high-efficiency cruise mode or low-speed high-torque mode, if a rapid acceleration driving operation signal is detected to exceed the third threshold, the second stator winding is immediately energized to temporarily switch the system into power assist mode.

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