Research Article

[Retracted] A Literature Review Research on Monitoring Conditions of Mechanical Equipment Based on Edge Computing

Table 2

Lossy compression methods.

Compression algorithm modelCompression algorithm typeAlgorithm titleAdvantagesDisadvantages

Single-algorithm compression modelQuantization-based compression algorithmScalar quantification [47]Simple method and fast processingDistorted data
Vector quantization [48, 49]Better than scalar quantificationLimited distortion
Compression algorithm based on signal decomposition (threshold processing)EMD [34]Fast signal decomposition and fast compressionEasy to generate IMFs overlap, resulting in signal distortion
Intrinsic time-scale decomposition [38]Better computational speed than EMD, high time–frequency resolution, the good compression effectDue to linear interpolation, it is easy to distort the intersection position
VMD [50]High decomposition accuracy, better decomposition of IMFs, accurate reduction of redundant informationWith boundary effects, the parameters have a large impact on the results
LMD [51]Better preservation of transient change information in the original signalStill has endpoint effects and does not have fast algorithms
Compression algorithms based on sparse dictionary transformations (complete and overcomplete dictionaries)STFT [52]Capable of fast time and frequency conversionLow resolution at high frequencies, resulting in signal loss during compression
DCT [53]Fast processing time and good sparse transformation effectThe transformation method does not work with all signals
DWT [54] and LSWT [55]With better time–frequency resolution, the LSWT algorithm does not consume memoryExcessive layer decomposition can result in wasted computational resources
Best orthogonal basis [56]Able to obtain near-optimal signal representationSparse is less effective when the signal cannot be represented by orthogonal components
Orthogonal matching pursuit [57, 58]Fast convergence to get a better sparse signalThe vertical projection of the processed signal is non-orthogonal and the number of iterations increases
Generalized morphological component analysis [59, 60]Capable of adapting to different input signal types, improving calculation speed and signal separation accuracyThe parameters of the calculation need to be set in advance, and the set values of the parameters directly affect the results of the processing
Neural-network-based algorithmRNN [43]Very strong nonlinear mapping, high compression ratio (CR)Requires training in the model and high computational resource requirements
Hybrid algorithm compression modelLossy single algorithm + lossless compression single algorithmBased on signal decomposition and Huffman [61]Furthermore, increase in CR, no secondary data loss due to the introduction of lossless compressionThis causes the complexity of the algorithm to increase and the data compression time to increase
Based on sparse dictionary transform and RLE [62]