Massage machine

What is this patent about?

’407 is related to the field of automated massage chairs, specifically focusing on the motor control systems used to drive treatment heads along complex, three-dimensional trajectories. In high-end massage equipment, motors must frequently switch between normal and reverse rotations and handle significant load fluctuations caused by the user’s body weight and movement. Traditional brushed motors capable of these tasks are often too bulky, while standard brushless motors can produce significant acoustic noise and vibration that disturb the user, especially when the massage heads are operating near the neck and head.

The underlying idea behind ’407 is to replace bulky brushed motors with compact, high-torque brushless DC motors while eliminating the noise and vibration typically associated with them. The invention recognizes that the discomfort caused by brushless motors stems from torque ripples and cogging when driven by standard rectangular waves. By implementing a sophisticated control strategy that forces the motor current into a sinusoidal waveform, the system achieves smooth, quiet operation even under the heavy, unpredictable loads inherent in a massage application.

The claims of ’407 focus on a control architecture for a three-axis massage mechanism that utilizes at least one brushless DC motor equipped with a rotation number detecting circuit. The system employs a control circuit featuring a rotation speed calculator, a speed controller, and a voltage controller that utilizes Pulse Width Modulation (PWM). Specifically, the claims describe overlaying a target sinusoidal waveform with a triangular carrier wave to define pulse widths based on their intersection points, ensuring the current delivered to the motor windings remains substantially sinusoidal despite varying mechanical resistance.

In practice, the invention manages the transition between different massage techniques by calculating motor speed based on the timing between Hall IC signals rather than relying on expensive external encoders. To maintain the sinusoidal current profile at low speeds or light loads—where pulses might otherwise vanish due to standard dead-time settings—the system can dynamically adjust the carrier frequency or the dead-time duration. This ensures that the motor does not stall or become noisy when the user shifts their weight or when the massage heads move to a different part of the body.

This approach differentiates itself from prior art by solving the startup and noise issues of brushless motors in high-load, variable-speed environments without the need for high-cost sensors. Furthermore, the invention optimizes the physical motor design, using an interior permanent-magnet (IPM) configuration or varied gap thicknesses between the rotor magnets and stator. These physical modifications work in tandem with the electronic control to ensure the counter electromotive force is naturally sinusoidal, resulting in a highly efficient, whisper-quiet massage experience that accurately follows intended hand-technique trajectories.