Servomotor Control via Integrated Communication Wire
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Solution Overview
Problem
Existing systems for controlling servomotors via electrical energy and control signals face issues such as energy attenuation due to unshielded networks, impedance mismatch, limited distance, and vulnerability to faults, which lead to communication breakdowns and high costs associated with shielded cables and redundancy.
Innovation Solution
The system integrates a communication wire into the power cable, electrically isolating it from phase wires at both ends, and uses frequency modulation with three frequencies to transmit control signals, allowing for a direct current supply and reducing the number of cables needed, while maintaining signal integrity and immunity to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If PLC system with series connection is used, then cable complexity is reduced, but signal attenuation increases and communication distance is limited
Solution Approach 1:
The patent introduces a differential communication mode using two dedicated communication wires as intermediaries to carry control signals. This mediator approach allows signals to be transmitted differentially between the two wires, rejecting common-mode noise and impedance variations from the power network, thus solving the signal attenuation problem while maintaining the simple series cable structure.
Solution Approach 2:
The patent replaces the traditional single-wire or shielded cable mechanical structure with a differential signal transmission system. By using two isolated communication wires carrying opposite polarity signals, the system substitutes the reliance on physical shielding and impedance matching with an electrical differential signaling approach, eliminating the need for expensive shielded cables.
2Object-affected harmful factors
If shielded cable is used for fieldbus, then signal immunity to interference is improved, but cost increases
Solution Approach 1:
The patent replaces the mechanical shielding approach with an electrical differential signaling system. By transmitting control signals as differential voltages between two isolated communication wires, the system achieves immunity to electromagnetic interference without requiring expensive shielded cables, thus reducing both material and installation costs.
Solution Approach 2:
The patent changes the signaling parameter from single-ended voltage relative to ground to differential voltage between two isolated wires. This parameter change fundamentally alters how signals are transmitted, making them inherently immune to common-mode noise and interference, thereby achieving the same protection as shielding but at lower cost.
3Reliability
If redundancy is implemented in fieldbus, then system reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces two isolated communication wires as intermediaries that provide inherent fault tolerance. The differential signaling between these two wires creates a naturally redundant communication path, where a single wire failure does not necessarily cause system failure, thus improving reliability without adding complex redundancy management systems.
4Ease of manufacture
If unshielded cable is used, then cable cost is reduced, but signal transmission quality deteriorates due to impedance mismatch
Solution Approach 1:
The patent replaces the reliance on precise impedance matching (a mechanical/electrical design constraint) with differential signaling. This substitution allows the use of simple unshielded cables without requiring controlled impedance specifications, as the differential mode inherently rejects impedance variations and noise, maintaining signal transmission quality at lower cost.
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 solution extends communication distances, enhances reliability by isolating signals from power, reduces cable complexity and costs, and improves immunity to interference, allowing for more stringent electrical network standards and fault tolerance.
Implementation Method 1
the signals are frequency modulated and comprise three frequencies, a carrier frequency and two frequencies representing respectively the numerical values '0' and '1'
Implementation Method 2
it includes electrical insulation at both ends of the communication wire, adapted to dissociate the signals from the power
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a system for controlling at least one servomotor from a command/control centre (9), of the type including a network for supplying power to the servomotor and means for transmitting electric control signals to the servomotor, from a command/control centre. The system according to the invention is characterised in that the signal transmission means are formed by a communication wire (7) built into the power cable (5). The invention can be used for controlling servomotors.