Machine Tool Braking With Energy Feedback and Brake Chopper Control
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Solution Overview
Problem
Existing machine tool braking methods, such as short-circuit braking, brake choppers, and recuperation, face issues with user safety, tool ergonomics, hardware requirements, and inefficient energy recuperation, particularly when rapid deceleration is needed.
Innovation Solution
A method for braking a machine tool that involves regenerative braking, feeding back electrical energy into the power supply device or intermediate circuit, and using a brake chopper to absorb excess energy when limits are exceeded, without requiring a separate controller, by adjusting the duty cycle and current space vector based on correction factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If recuperation is used to brake the machine tool, then electrical energy is fed back into the power supply device, but the power supply device may exceed its limit values for absorbing electrical energy
Solution Approach 1:
The control unit continuously monitors the electrical energy released during braking and compares it with the power supply device's absorption limits. Based on this feedback, the control unit dynamically adjusts the braking torque to ensure the released energy does not exceed the power supply device's capacity, thereby preventing damage while maximizing energy recuperation.
Solution Approach 2:
The braking torque is dynamically adjusted during the braking process based on real-time monitoring of the power supply device's energy absorption capacity. The control unit modifies the braking characteristics adaptively, transitioning between different braking modes (recuperation, regenerative, and mechanical braking) to optimize both energy recovery and device protection.
2Reliability
If a brake chopper is installed to absorb excess braking energy, then the power supply device is protected from damage, but the machine tool's weight and volume increase
Solution Approach 1:
The control unit utilizes existing components (motor, power electronics, sensors) already present in the machine tool to perform the function of energy management during braking. By intelligently controlling the motor's operating mode and coordinating with the power supply device's capabilities, the system protects itself from damage without requiring additional dedicated braking components.
Solution Approach 2:
The motor serves multiple functions: it acts as both a drive motor during operation and as a generator during braking to recover energy. The power electronics that originally served only for motor control are also utilized for managing regenerative braking and coordinating with the power supply device, eliminating the need for separate brake chopper hardware.
3Speed
If short-circuit braking is used, then rapid deceleration is achieved, but the machine tool's electronics must handle high initial short-circuit currents
Solution Approach 1:
The braking process is dynamically controlled with continuously adjustable braking torque, transitioning smoothly from maximum recuperative braking to mechanical braking as needed. This dynamic control avoids the abrupt current spikes of short-circuit braking while maintaining effective deceleration performance.
Solution Approach 2:
The control unit prepares for the braking process in advance by pre-coordinating with the power supply device to establish its energy absorption capacity. This preliminary preparation allows the system to absorb the braking energy gradually through controlled recuperation, cushioning against the shock loads that would otherwise damage the electronics.
4Reliability
If the braking process is performed slowly to avoid exceeding power supply device limits, then the power supply device is protected, but user safety is compromised in rapid deceleration scenarios
Solution Approach 1:
The braking process is segmented into multiple phases: initial recuperative braking to maximize energy recovery, followed by mechanical braking when the power supply device approaches its absorption limits. This segmentation allows the system to protect the power supply device while still achieving rapid overall deceleration through the coordinated action of different braking mechanisms.
Solution Approach 2:
The braking system combines multiple braking mechanisms (recuperative braking, regenerative braking, and mechanical braking) into a composite braking solution. Each mechanism contributes to the overall braking performance, allowing the system to achieve both power supply device protection and rapid deceleration for user safety.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables rapid, safe braking with efficient energy recuperation, reducing tool size and weight, and minimizing power loss, while protecting the power supply device and user from damage.
Implementation Method 1
During the braking process, the motor (12) is braked in a controlled manner and thus becomes a generator
Implementation Method 2
The brake chopper (18) has a duty cycle D, which is determined by the correction factor kRed, in order to absorb an amount of electrical energy
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
The present invention relates to a method for braking a machine tool (10), wherein the machine tool (10) is a battery-powered or mains-powered machine tool and has a brake chopper, and electrical energy released when braking the machine tool (10) is fed back at least partially into a power supply device (14) or an intermediate circuit of the machine tool (10).